Aggression Frequency vs. Total Aggression

On Pokertracker, what are the definitions of aggression frequency and total aggression? Where do you suggest these numbers should be? How should I use these stats to my advantage? How should they change with position? Thanks!

There's a good article somewhere on "How to use poker tracker". I'm sure it wont be hard to find. It's long, but it's very useful and details what most of the important stats are.

AF is the stat that tries to do too much, it's the amount of times a player raises or bets divided by the amount of times they call or check. If yours is under 2, you're either calling too much or not betting enough. If your opponent's is above 4, they probably cbet too much post flop, you can sometimes call or raise their flop and turn bets lighter. If your opponent's AF is lower than 1.5 or so, when they bet and raise you can believe them, because that doesn't leave much room for bluffs.