it has a large array of players whose profiles are meticulously designed, all of which would fall under variations of your standard tight/loose+passive/aggressive descriptions. you can customize behavior very specifically (e.g. if it's 3bet to you in the sb and you have exactly 22, reraise 65% of the time but otherwise fold) and save the player off as your own character.
there are a number of default lineups for low limit types, passive types, loose aggressive types, average types, etc which contain a pre-built mix of the above-mentioned players. you can change the lineup as you wish to make your own lineups to match a specific type of game (e.g. 6 loose/passive, 2 maniacs, 1 tight/aggressive, 1 weak/tight).
suffice it to say, it's exceptionally flexible.
www.wilsonsoftware.com (and no, i don't work there!)