I use it as a funny way to call my friend Mark haha. But the actual game is that there is a group of people (2 or more) in a big dark room and one person is 'it'. Everyone spreads out and the game begins, everyone has to yell 'Marco!' to which the it person replies 'Polo!' until by following their voice, somebody finds and tags the it person. Then that person wins!
The same point of every other game in the entire world: entertainment. The goal is the same as in "Tag".
Ok, i get it, thanks