In poker, the act of making the first non-zero bet in a betting round is called opening the round. On the first betting round, it is also called opening the pot. Some games may have special rules about opening a round that may not apply to other bets (for example, they may have a betting structure that specifies different allowable amounts for opening than for other bets, or they may require a player to hold certain cards to open).
The term is also used to describe a category of poker game in which some cards held by individual players are visible to all other players, either by being dealt face up or by being exposed during play (but before showdown). Most forms of stud poker are open poker (blind stud games are an exception). Most forms of draw poker, in contrast, are closed games because no player's cards are seen until showdown (draw games with a rollout are an exception). Most community card games like Texas hold'em are considered closed as well, because the only cards exposed before showdown belong to everyone; the individual players' cards are never seen until showdown.
