Go to User CP and it will show who repped you. As for what it is... its basically a system designed to reward posters for good posts. You can give out rep to anyone. Its pretty meaningless and ends up getting abused, but its there for you if you want it. You can also turn it off.
Well, Basically you get 1 rep Point for every year you have been here. And you've been here for 3 years so 3 rep. Also every 10,000 Posts = 1 rep and of course Peer Voting adds to rep as well
You haven't been peer repped yet. I just repped you Legacy... so now try going to User CP and see if it shows up. Its in the middle of the screen.
There are 2 parts to the rep numbers. The first is Rep Power which is what is displayed under each user's avatar. That is how much you can increment another user's rep points. The second is Rep Points and this is displayed for each person in your UserCP. To me, I see rep as a way to provide feed back to fellow posters about their posts
Better explanation is there's two components - rep power and rep received. rep power is what you give to other people when you rep them. rep received is the rep power of the person giving you rep.
You're right, I should make it 100 The way the system is set up, admins rep power doesn't increase, no matter how much rep we receive.
There is no max. However, I did change the defaults so that rep power won't going spiraling out of control right away.