English: I think you mean your friend knows one of the presenters.
Czenglish: Yes! So what is a moderator, then?
A moderator is the person who checks, edits, or presides over something to make sure it runs smoothly. That could mean anything from the person who supervises an exam, to the person in charge of an internet chat room.
A moderator is definitely not the person who presents a television show though – that is a presenter.