There are four basic statistics that can tell you how’s the playing style of a particular player:
VP$IP(Voluntarily Putting money In the Pot) – It’s the % of times the player is in a pot. For example, a 40% VPIP means the player is in 40% of the pots. This measures the looseness of a player pre-flop: if a player calls 40% of the hands preflop, he’s a very loose player and it’s highly likely that he’s a bad player. For full-ring tables (10 players), a VP$IP of 10%-20% is considered tight. A VP$IP of 30% or more is very loose.
VPIP has another good use: comparing this to the preflop-raise we can get a good idea of how a player plays depoqq preflop.
PFR(Preflop raise) – It’s the % of times the player raises preflop. It’s useful to compare this stat to VPIP. Obviously, VPIP will always be higher or equal to PFR, because VPIP counts calling and raising preflop.
When there’s a big difference between VPIP and PFR (for example: VPIP = 20%, PFR=3%) you can assume you’re dealing with a player that plays passively preflop. When the difference is 4% or less (for example VPIP=20%, PFR=16%), and the VP$IP is in a standard value range (15%-20% for full-ring, a bit more for shorthanded) you can assume you’re playing against a tight-aggressive player (TAG), which are the players who profit the most on low and medium stakes. You should be a TAG yourself, it’s more than proven that it’s the playing style that profits the most, and works for low, medium and high stakes.
AF(Aggression factor) – It measures the post-flop aggressiveness of a player. It should always be compared to VP$IP: a player that is on many pots won’t usually have a high AF, simply because many times that player will have trash, and won’t have a made hand or a draw to play with. This will tell you how much you should respect a player’s bets.
For example, a player with 20% VP$IP and 5 to 10 AF is considered an aggressive player, and will usually make a continuation bet on you, and may try to bluff in other spots.If that same player had 0.5 AF, he was a passive player, so you should usually respect his bets.
A player with 50% VP$IP and 1 AF, looking only at the AF, looks passive. But don’t forget you have to look at VPIP too, and this player is clearly aggressive because of his very high VPIP and 1 AF.
Hands – This is simply the number of hands you have of a particular player. You should always have 20 or more hands to look at VPIP and PFR. To look at AF you should have 50 hands or more.