There is a common misconception that this role is the same as a home loan originator. In order to provide a mortgage to borrowers, the originator organizes all of the paperwork. Underwriters review all of that paperwork to ensure everything is in order and that borrowers are truly eligible for such a loan.
Underwriters will notify the originator if something is wrong with a candidate. They look at everything- credit, assets, bank statements, W2s- to determine your loan worthiness.