Below are straight from the box scores/stats:
P/G = Points Scored/Game
P/Ps = Points Scored/Possession (avg number of points scored each offensive/special teams possession)
Def. P/G = Points Allowed/Game
Def. P/Ps = Points Allowed/Possession (avg number of points allowed each defensive/special teams possession)
Net P/Ps = Points Scored (or Allowed if negative)/Possession (avg points gained/lost every possession)
These are adjusted stats (They are adjusted to a common baseline [the "average" FBS opponent] by taking into account the opponents stats relative to the mean.):
Adj. P/Ps = Adjusted Points Scored/Possession (essentially expected P/Ps against an average FBS defense)
Adj. Def. P/Ps = Adjusted Points Scored/Possession (essentially expected Def. P/Ps against an average FBS offense)
Adj. Net P/Ps = Points Scored (or Allowed if negative)/Possession (essentially expected Net P/Ps against an average FBS offense)
WQ = Win/Loss Quality (A measure of "quality" based on actual accomplishments. You get more credit for beating a "good" team than losing to one, and less penalty for beating a "bad" team than losing to one. In a sense this is like a strength of schedule measure, but I dislike the common idea that simply losing to good teams means that you "might" be good. You need to actually beat a good team for a strong schedule to matter. The result is scaled to be a max of 1 each week).
Rating = Expected Win%. (Given an Adj. Net P/Ps its pretty easy to project an expected win% against an average team. To this expected win% a bonus is added based on WQ. The actual real-life win% for the team is accounted for as well to come up with the final rating).