User blog comment:Planterobloon/Character stats/@comment-5294711-20121231162056/@comment-4418057-20121231224728

I'd be inclined to say go to d20srd.org, but I'll put it here anyway. Levels are character levels, gained by beating monsters. When you go up a level, you become more powerful, possibly gaining a class feature as shown in the Classes section of that site I'm talking about. By default, anyone above 10th level is high-level.