.sdf什么文件。它与。mdf文件的区别。它与linq到Sql一起工作吗?

I am playing with wpf and when i have created database it is created with the .sdf files. I want to know details of .sdf files. How it is different then the standard .mdf files and will they support linq to sql? Because i am not able to use it with linq files.I am playing with wpf and when i have created d