AF is the ratio of bets + raises to calls. So if a player has an AF of 1, they make the same amount of bets + raises as they do calls. If you've seen someone make 25 bets, 15 raises, and 10 calls on the flop, their flop AF will be 4.0 ((25+15)/10).
AFq is (# of bets + # of raises) / (# of bets + # of raises + # of calls + # of folds).
So it's the number of their aggressive actions expressed as a percentage of their total actions.
AF can be harder to interpret because a nit could have a high AF just because he plays fit/fold postflop and only plays 15% of his hands, and this could lead you to think he is a maniac, but he really isn't. AFq gives you a clearer idea of someone's aggression.