An employer registers, builds a company profile and posts a job from the job form. They see their jobs and the applications on them in an employer dashboard, and they can move applicants through the application list and board. In the free plugin the stages are fixed; custom hiring stages on the board are a Pro feature.
A candidate searches and filters the listings, opens a role and applies. Because BuddyNext is part of the install, the candidate also has a profile, and the employer has a presence in the feed. A job board without that is a list of links people visit once. With it, there is a reason to come back between searches: to follow a company, to ask a question, to see who else is active.
Resumes and resume search are Pro, as are job alerts. If you want employers to search candidates, or want candidates to get an email when a matching job is posted, that is the upgrade to plan for.