Code snippets are ready-made snippets of code you can quickly insert into your code.
Eg: snippet for Console.WriteLine, just type:
cw and then tab tab.
 
 
Eg2: insert class property, just type:
prop and then tab tab.
 
Outputs:

 
 
Eg3: insert incrementing loop, just type:
forr and then tab tab
 
Outputs:

 
 
Eg4: creating constructor and creating a private field automatically:
To create constructor automatically, type:
ctor + tab + tab
 
To create a private field automatically, type:
ctrl + .
And then press enter on the line of code that you want to use from a list of available options:
 
Eg: generating a constructor and private field shortcuts:

 
 
 
Default code snippets:
By default the following code snippets are included in visual studio for c sharp:
Name (or shortcut)     Description                                                        Valid locations to insert snippet
cw 	               Creates a call to WriteLine.                                       Inside a method, an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
if                     Creates an if block.                                               Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
                                                                                          
else                   Creates an else block.                                             Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
                                                                                          
switch                 Creates a switch block.                                            Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
                                                                                          
                                                                                          
while                  Creates a while loop.                                              Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
for                    Creates a for loop.                                                Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
foreach                Creates a foreach loop.                                            Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
forr                   Creates a for loop that decrements                                 Inside a method
                       the loop variable after each iteration.                            , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
                                                                                          
do                     Creates a do while loop.                                           Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
                                                                                          
                                                                                                                                                                                    
#region                Creates a #region directive and a #endregion directive.            Anywhere.
#if 	               Creates a #if directive and a #endif directive. 	                  Anywhere.
~                      Creates a finalizer (destructor) for the containing class. 	      Inside a class.
checked                Creates a checked block.                                           Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
class                  Creates a class declaration.                                       Inside a namespace
                                                                                          (including the global namespace) 
                                                                                          , a class, or a struct.
                                                                                          
prop                   Creates an auto-implemented property declaration.                  Inside a class or a struct.
propfull               Creates a property declaration with get and set accessors.         Inside a class or a struct.
propg                  Creates a read-only auto-implemented property                      Inside a class or a struct.
                       with a private set accessor.
                                                                                          
ctor 	               Creates a constructor for the containing class.                    Inside a class.
indexer                Creates an indexer declaration.                                    Inside a class or a struct.
equals                 Creates a method declaration that overrides                        Inside a class or a struct. 
                       the Equals method defined in the Object class. 	
attribute              Creates a declaration for a class that derives from Attribute.     Inside a namespace 
                                                                                          (including the global namespace)
                                                                                          , a class
                                                                                          , or a struct.
enum                   Creates an enum declaration.                                       Inside a namespace 
                                                                                          (including the global namespace)
                                                                                          , a class
                                                                                          , or a struct.
                                                                                          
struct                 Creates a struct declaration.                                      Inside a namespace 
                                                                                          (including the global namespace)
                                                                                          , a class
                                                                                          , or a struct.
                                                                                          
                                                                                          
using                  Creates a using directive.                                         Inside a namespace 
                                                                                          (including the global namespace).
                                                                                          
                                                                                          
                                                                                          
namespace              Creates a namespace declaration.                                   Inside a namespace
                                                                                          (including the global namespace).
try                    Creates a try-catch block.                                         Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
tryf                   Creates a try-finally block.                                       Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.                                                                                          
exception              Creates a declaration for a class                                  Inside a namespace 
                       that derives from an exception (Exception by default).             (including the global namespace)
                                                                                          , a class
                                                                                          , or a struct.
interface              Creates an interface declaration.                                  Inside a namespace
                                                                                          (including the global namespace)
                                                                                          , a class
                                                                                          , or a struct.
invoke                 Creates a block that safely invokes an event.                      Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
iterator               Creates an iterator.                                               Inside a class or a struct.
iterindex              Creates a "named" iterator                                         Inside a class or a struct. 
                       and indexer pair by using a nested class.
lock                   Creates a lock block.                                              Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
mbox                   Creates a call to System.Windows.Forms.MessageBox.Show.            Inside a method
                       You may have to add a reference to System.Windows.Forms.dll.       , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
sim                    Creates a static int Main method declaration.                      Inside a class or a struct.
svm                    Creates a static void Main method declaration.                     Inside a class or a struct.
unchecked              Creates an unchecked block.                                        Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
unsafe                 Creates an unsafe block.                                           Inside a method
                                                                                          , an indexer
                                                                                          , a property accessor
                                                                                          , or an event accessor.
 
 
 
For more information, see here.