L (Loose), sL (semi-Loose), and T (Tight) are pre-flop measures.

sL means Semi-Loose--plays more hands than a "tight" player, less than a "loose" or "extra-loose" player pre-flop.

A (Aggressive) and P (Passive) are post-flop measures.

A (Aggressive) means that a player is more likely to bet/raise than just call post-flop.
P (Passive) means that a player is more likely to just call rather than bet/raise.

Aggression post-flop is figured by taking the total number of bets and raises and dividing that number by the number of calls:

(Bets+Raises)/Calls= Aggression Factor (AF)

Glad I could help. Also, check out excession's Poker Tracker pages on the front page....

But why does it say AA or PA or PP? Why does it state it twice?

The default auto-rate rules provided with PT also track pre-flop aggression, which is pretty much just how much someone raises pre-flop.

Excession's rules are much better.

If someone is TAA, they are tight pre-flop, aggressive pre-flop (PFR >6%), and aggressive post-flop.

Read excession's