What do they ask in background check?

[DesiOPT-FaceBook-Admin]

My friend recently got an entry level Full time job in a big company. -What do they ask in the background check exactly?
Do we need to have all the documents?
-I heard that they just call your employer or will there be a detailed check with SSN?
-What if the information does not match (prior employment history)?

This was posted on https://www.facebook.com/desiopt1 on July 4th 2013

[DesiOPT-FaceBook-Fan]

they do drug test, criminal check

[DesiOPT-FaceBook-Fan]

information mismatch of previous employment its because you lied, and that could cost you your job! thts the reason they want to conduct these checks to make sure that you are the person you are claiming to be on your resume!

[DesiOPT-FaceBook-Fan]

Drug test, criminal records check of all counties you lived in, employment verification & your driving history if required... employment verification is not as detailed as its in india but its done to check if details provided are correct or not.