As you know under user setup you can give a user, resource, or administrator specific module settings for a site(s). For example, under a user profile, you choose the User Group and underneath that, you can select User Authorization Groups for the modules Standard Work/Documents, Scheduler, Work Orders, Spares, Production, Skills, and Lean Tools. Also if you are an Admin you can grant or remove permissions under each module setting as well.
Something you need to be aware of in user setup is what sites a user has access to, the reason being that if a user, resource, or administrator has certain permissions under User Authorization Groups and they have access to more than one site, that user has those same permissions on all sites. If you remove certain permissions from one site, it will remove those permissions from all sites associated with that user.