KentZhou:

What's the difference between Entity framework and LINQ to SQL?

Here is discussion by David Hayden on the difference and when to use it.

It may be worth reading this article as well.

Let me know further queries.

Thanks,

LINQ to SQL supports rapid development of applications that query Microsoft SQL Server databases using objects that map directly to SQL Server schemas. 

LINQ to Entities supports more flexible mapping of objects to Microsoft SQL Server and other relational databases through extended ADO.NET Data Providers

http://blogs.msdn.com/data/archive/2007/04/28/microsoft-s-data-access-strategy.aspx