MyBB Community Forums

I know yes overrides no, but unsure how add. groups & forum permissions factor in; give me the full synopsis please.

Let me clarify:

I know that yes pverrides no and forum permissions override usergroup permissions; what I don't really understand is how additional groups factor into all these permissions and what not (oh yeah, mod perms override forum usergroup perms)

Which group/forum permissions do you exactly mean? I don't think the override behavior is fully consistent across all of them.

How does additional groups affect permissions? I mainly mean permissions for forums;; the local forum permissions override usergroup permissions with yes > no.