Yes the witnesses are the ones that are like the politicians. The top 21 of them get to decide what rules we operate by. In order for anything to change, these top 21 people have to agree (or a large percentage of them)... We all get to vote for them, but the votes are weighted by size of your SP. If you have a small amount like me, then you can vote but the big guys are the ones who really pick which witnesses are at the top.

Does that answer your question, or would you like a further explanation?