Every candidate will have confusion that Can employers look up employment history? Do they ask your previous employer about joining date, position, job title, job description etc.
Employment verification is a process which every employee requests current employer or previous employer to provide details of his employment .
There are plenty of reasons for background checks to fail.
Hiring managers/HR do a lot of background check and some of them are following
Employers check original certificates of education while joining from candidate, they verify according to the resume.
Companies check background verification against candidates resume. This can be done by contacting last employer of employer.
Most of the time, employers trust that potential applicants have their claims degrees.. they ask applicants to showcase their original degree for cross checking.