rules
Table stakes
The rule that you can only wager the chips in front of you at the start of a hand — no reaching into your pocket mid-hand, and no being bet out of a pot you cannot cover. It is why side pots and all-ins exist, and it applies in every regulated poker game.
Example. Under table stakes, a player with $50 who faces a $200 bet can call all-in for $50 and win only that much from each opponent.