In poker, there are three types of betting limits - limit, pot-limit and no-limit. The limit placed is on the amount any player can bet or raise at any one time.
Limit poker is the most common form of poker. A fixed limit is placed on the amount a player can bet or raise.
For example, in a $3/$6 Limit Texas Hold'em game, the maximum bet/raise amount is $3 during the first 2 betting rounds (Preflop and Flop) and $6 during the last 2 betting rounds (Turn and River).
In a pot-limit poker game, the maximum amount a player can bet is equal to the size of the pot at the time.
Number of raises per betting round
Besides limits on the bet/raise amount, there is also a limit to the number of raises in a betting round. Usually, up to 3 raises per betting round is allowed.
In a no-limit poker game, a player can bet all his chips on the table at one go.