The reputation system is very similar to the Karma system seen on other popular websites and forums (Slashdot.org, for example). Its purpose is to hopefully give users an idea of how respected, knowledgeable, helpful, gracious, etc., a person is. It is a system in which you rate your peers. It is a system that, hopefully, will make you think twice about your posts. Eventually, people with higher reputation scores will enjoy a few forum 'perks'; more storage for private messages, for example.