The employer may want to make sure you are telling the truth. It's estimated that up over 40% of resumes can contain false or tweaked information, so, employers want to ensure that what they are getting in an employee is what they were promised. The employer may perform a background check to find out whether you actually graduated from the college you said you did or to confirm that you worked at your previous employer(s) during the time stated on your resume or your job application.