What is the difference between using a DataContext instance in the following two ways?

Question

Hi,

First post here, so pardon me if its a repeat qossion... :)

Can someone please tell me what is the difference between creating the datacontext as -

1. MyDatabaseDataContext db=new MyDatabaseDataContext();

//////
///////// Some code/


2.using (MyDatabaseDataContext db=new MyDatabaseDataContext())

{
 ///
////// do something.
}