Texas Hold'em is typically played with 8 to 10 players. Limit Texas Hold'em uses a structured betting system, where the amount of each bet is strictly controlled in each betting round (In Open or No-limit Texas Hold'em, there are no restrictions on the size of bets; a player may wager any amount, up to their entire stack, at any time.) There are two denominations of bets, called a small bet and a big bet, which in this program is $10 and $20 by default. In the first two betting rounds, all bets and raises are $10, while in the last two rounds, they are always $20. In general, when it is a player's turn to act, one of three betting options is available: fold, check/call, or bet/raise.
A check and a call are logically equivalent, in that the betting level is not increased. The term check is used when the current betting level is zero, and call when there has been a wager in the current betting round. Similarly, a bet and a raise are logically equivalent, but the term bet is used for the first wager of a betting round.
There is a maximum of three raises allowed per betting round. The betting option rotates clockwise until each player has matched the current bet, or folded. If there is only one player remaining (all others having folded) that player is the winner and is awarded the pot without having to reveal their cards.
Darse Billings, Aaron Davidson, Jonathan Schaeffer, Duane Szafron. The Challenge of Poker, Artificial Intelligence, 2001.
http://www.cs.ualberta.ca/~darse/Papers/AIJ02.html