The reputation is represented by the Green bars under our names. If you post something helpful people can add to your reputation or if bad they can take it away (everyone can vote either way using the scales under the members name by their post). You also earn repuation by starting new threads and posting messages plus every month you have been a member means you get more reputation. I hope that helps?
Overall its just a way of seeing who the regular helpful members are and who is new. Its interesting to note that no one has earnt a bad reputation on here yet.
