Pot limit

A game played with a pot-limit betting structure allows any player to raise up to an amount equal to the size of the whole pot before the raise.

For example, let us assume that there is $10 in the pot at the start of a betting round. The first player may open the betting for up to $10. If he does in fact open for $10, the next player may raise to $40 (after calling the $10 bet, the total amount of the pot is $30, so he may raise $30). The third player would be entitled to raise to $140 (after calling $40, the pot would contain $100, thus he may raise $100). Any player may also raise less than the maximum so long as the amount of the raise is equal to or greater than any previous bet or raise in the same betting round.
Some pot-limit games make exceptions to the method described above when calculating the maximum raise in the betting round before the flop:

Some structures treat the small blind as if it were the same size of the big blind in computing pot size. In such a structure, a player can open for a maximum of four times the size of the big blind. For example, if the blinds are $5 and $10, a player may open with a raise to $40. (The range of options is to either open with a call of $10, or raise in increments of five dollars to any amount from $20 to $40.) Subsequent players also treat the $5 as if it were $10 in computing the pot size, until the big blind is through acting on the first betting round.
If the action folds all the way around to the small blind, the maximum amount the small blind can raise is also not universally agreed upon. Some games treat the big blind as a "raise" of the small blind for the purpose of calculating the maximum raise—the small blind is allowed to call the big blind, and then make a pot sized raise of twice the big blind, for a total bet of three times the big blind. Other games treat the blinds as dead money for the purpose of calculating the raise, and allow the small blind to make the same size raise as any other player, i.e. a total bet of three times the big blind plus the small blind.
Because of the disparity in methods of calculation, and the fact that the issue is certain to come up often, most major tournaments will announce the amount of the maximum opening raise to all players any time the betting limits are increased.

World Series of Poker

Razz has been an event at the World Series of Poker since 1973, when Sam Angel won the first event for a grand prize of $32,000. The Razz event does not draw the larger numbers of players that more popular games like Texas hold 'em do. The Razz tournament was televised by ESPN in 2004.,
London lowball is a game played almost exclusively in Europe. It is almost identical to Razz in play with the following exceptions: straights and flushes count against a player for low, so the best possible hand is 6-4-3-2-A, and its canonical version is played at pot limit. Some variations of the game are played at no limit, but the name "London lowball" is typically reserved for the pot-limit version.
Normally the best starting hand in Razz is A-2-3. A general strategy in a full-ring game is to only play three card 8s or lower, meaning any three cards 8 or lower that are not paired. Players want to avoid making pairs and should evaluate other door cards in relation to the strength of their hand. For instance, Jane holds 3-4-5 and sees four "dead" door cards of 3-4-4-5 behind her. This is a strong hand, as the likelihood of pairing her hole cards is now greatly diminished.

Another key strategy in Razz is stealing the antes and bring-in bets. If a player is to the right of the bring-in bettor, and everyone else folds, a raise with a lower exposed card is normally the correct play. For example, if Mary has a 9 showing, and John, the bring-in bettor, has a K showing, Mary should normally raise if everyone else folds.

Lowball (poker)

Some forms of poker, often called lowball, sometimes called low poker, reward poor poker hands (in the traditional sense). There are three common variations on this idea, differing in whether aces are treated as high cards or low cards, and whether or not straights and flushes are used. The methods are:

Ace-to-five low: The lowest possible hand is 5-4-3-2-A, called a wheel. Aces are low and straights and flushes are ignored. This is the most common method.
Ace-to-six low: Also called 6-4 low, since the lowest possible hand is 6-4-3-2-A. Aces are low and straights and flushes count as high hands.
Deuce-to-seven low: Also called 7-5 low, since the lowest possible hand is 7-5-4-3-2. Almost the direct inverse of traditional "high hand" poker. Aces are high and straights and flushes count as high hands. Since aces are high, A-5-4-3-2 is not a straight, but just ace-high no pair.
Deuce-to-six low: The other, mostly unused, possibility would be 6-5 low. Aces are high, straights and flushes are ignored.
Some examples of lowball games are:

California Lowball: Draw poker played with A-5 ranking, usually with limit betting, one joker in the deck.
Kansas City Lowball: Draw poker played with 2-7 ranking, usually played no-limit.
Razz: Seven-card Stud, A-5 ranking.
Triple Draw: Draw Poker with three drawing rounds, played limit (or occasionally pot-limit), with either A-5 or 2-7 ranking.
London Lowball: Seven-card stud with A-6 ranking and pot-limit betting.
Some games are played high-low split, where the player with the best traditional poker hand (called the "high hand") splits the pot with the best low hand. The low hand is decided by one of the methods above. Nearly every common split-pot game uses A-5 ranking, often with a qualifier for low, in which only an 8 low or better is eligible for a pot. Low hands tie more frequently than high hands, especially in community card games, so it is not uncommon for such a hand to win a small fraction of a poker pot. For example, if one player has the high hand on showdown, and two other players tie for the best low hand, the high hand wins half of the pot and each low hand wins only a quarter of the pot. Playing ace-to-five high-low greatly increases the chances of the "scoop"--winning both hands--because a low flush or straight may count for both high and low. See Rule variations (poker)

Chinese poker can be played with the middle hand played for low.