It's nothing terribly exciting I'm afraid - it's just to indicate your "seniority", if you like. So I have lots of pips because I'm the Master
You get more pips by posting more - 50 posts is the first benchmark. If I were operating a more advanced version of the forum I could probably limit things on the basis of seniority but there isn't much more to it really. Except that I get to decide what everyone gets called as they progress!