Candidate Search functionality - searching only fields, or also attached resume?

Candidate Search functionality - searching only fields, or also attached resume?

When you run a Search in Recruit, is it only searching in the database fields, or is it also searching in the attached resume? I seem to be pulling up candidates who only have the search term in their resume, not in any field. If so, does the resume have to be in a certain file format for it to search it, or does it auto search in any file type?