Hi Mark,
There's a system on the forums where each registered user's account has a peer-review rating referred to as "reputation", the number you see in the top right of each post labelled "Rep Power". In the lower left of each post there's a little six-pointed, sheriff's badge kind of star where you can either add to or subtract from the poster's "rep power". Every registered user can do this to any other registered user, for whatever reason they choose. So in effect, it's just an indicator of whether the person's posts are useful, helpful, friendly, cool, etc, cause I don't think rep can fall below zero, and every account starts at zero.
I noticed you've been very helpful and informative with your posts so I felt you deserved a +1, that's all.