Pot limit and No limit
There are two pot variations that are commonly seen: Pot Limit and No Limit.
No Limit games are often applied to Texas Hold 'em and Pot Limit to Omaha. However, there is no real reason why you cannot play any poker using any of the pot variants listed below.
Pot Limit games are just that. Players can bet anywhere between the current limit of the table (The Lower Limit during the Pre-Flop and the Flop and the Higher Limit during the Turn and the River), and the maximum amount in the pot and on the table.
For example: We join a 20/40 game during the Flop. There is 200 USD in the pot and the player in the Small Blind position has made a 20 USD bet. The next player would need to bet 20 USD to call. Making the total pot 240 USD (200 (Pot)+20 (1st Player's Bet)+20(Your Call)). In this case, you can raise by up to 240 USD.
For instance, you raise by 160 USD. Now there is 400USD in the pot. The next player must at least call your 180 USD bet. This would mean there is now 580 USD on the table (200 (Pot)+20(1st Player's Bet)+180 (Your Bet and Raise)+180 (Next Player's Call). He may raise by anything between the table limit (Lower or Higher, in our example 20 USD or 40 USD) and 580 USD.
As you can see, the pot size increases exponentially and, because of this, this type of poker may sometimes be considered closer to a No Limit game than a Fixed Limit one.
Quite simple, as the name implies, in a No Limit game, players can bet anything between the limit of the round and their total amount of chips. Betting all your chips, in any poker game is called going 'All In'. This could be because you choose to raise by the full amount of your chips, or because you simply have run out of chips during that particular hand.
Note: Rebuying chips DURING a hand of poker is strictly prohibited.
If, during a hand, a player runs out of chips, but other players continue to bet, then the pot is split at the point the player bet all his chips. All subsequent bets made by the other players are kept in a separate "Side Pot". At the Showdown, the original player is only competing for the Main Pot, the one that he contributed to. All other players are competing for BOTH pots. In a land based environment, the winner of the side pot is determined first.
Occasionally, you may see several side pots. Again, the same rules are applied here. Once again, players only compete for the pot(s) that they have contributed to.