Betting Structures
While poker games have been known to run the gamut of betting traditions as players and the game change over time, a few major methods have become the standard for poker game play, especially in tournaments both online and off. Bets are usually made in increments known as a betting unit: depending on the buy-in and type of game, this can range anywhere from one cent to a hundred dollars (or more). The higher the stakes of the game, the larger the betting units generally are.
Here are the most common betting structures that you'll find in poker games today:
No Limit

No limit poker is exactly what it sounds like: there's no limit to what you can bet, so you can go all-in at any point. This opens the doors for bluffing, protection, and slow-playing, and it makes watching your opponents essential. While the betting structure is easy to understand-- bet what you want whenever you want (provided you're still following the rules of poker!)-- this type generally requires a more nuanced understanding of poker strategy in order to be successful.
Pot Limit
While the concept of pot limit is easy enough to understand, a lot of people avoid it in casual games and play with this kind of betting structure only when there's someone (a computer or a designated individual during a tournament) who will do the counting for them. Since pot limit means that you can bet up to the current amount that's in the pot, if you're sitting at a large table on a hand with a lot of action, keeping track of how much is there can be intimidating, especially if bets and raises come in quickly. Since some house rules require the dealer to return your chips to you if you bet too much and some don't, it's important to know the rules of the house before you sit down and the amount in the pot before you bet.

So what makes up the pot? The pot consists of three things:
- Chips from previous rounds
- All the money that's been put into the pot on the current round by players before the one making the bet
- The betting players "call" before making a raise.
Let's look at how pot limit works over the first two rounds of poker play at a $5/$10 table with three players:
Round One
This is the first round, so there's no starting pot.
- Player A: $10 bet (Pot limit is now: $10.)
- Player B: Calls. (Pot limit is now: $20-- $10 from Player A and $10 from Player B.)
- Player C: Calls and raises $5. (Pot limit is now $35-- $10 each from A, B & C, and a $5 raise from C.)
Assuming that there is no other action on this round, the final chip count in this round is $35. Since the starting pot for a round has the chips from previous rounds, Round Two now has a $35 starting pot.
Round Two
- Player B: Checks. (Pot limit is $35-- amount of starting pot)
- Player C: Declares "pot" (bets the pot limit). (Pot limit is now $70-- starting pot + Player C's raise of $35.)
- Player A: Calls. (Pot limit is now $105-- starting pot + $35 bet from Player C and $35 from Player A.)
With lots of players deeply involved in the action, following this can be quite difficult, which is why most houses allow players to check with the dealer for the pot limit, and many tournaments post the small blind, big blind, minimum and maximum bet allowed near the tournament clock.
Fixed Limit

Fixed Limit betting is the easiest type to understand, because there's no calculation involved as in pot limit (where you need to know how much is in the pot) or no limit (where you need to plan your raises and checks in accordance with the other players). In fixed limit, you either bet, or you don't-- the amount is determined for you. This doesn't leave much room for manipulating the other players, either through a bluff or by forcing weak-handed players out, so many casinos will allow for a big bet during later rounds. The big bet offers players the option of either making the normal fixed bet or making the big bet (generally twice what the fixed bet is). The limits in fixed limit apply to each bet, not each round of betting, so re-raises are possible.
Spread Limit

This particular betting structure is far less common than the other three. It consists of a range of bets (a spread) which can be bet. Examples include a $1 to $5 spread, as well as much wider ranges, such as $10-$1000. Smaller spreads make it difficult to get other players to fold by making a large wager and also tend to weed out weaker players who cannot mask their tells and will instead bid in predictable ways (large bets on strong hands and small or no bets on weak ones).
Large spreads, such as the previously mentioned $10-$1000, are referred to as the "California Spread," so named because this betting scheme is popular in California casinos where no limit poker was forbidden by law. The maximum limit is the same as the max buy-in, which creates a first hand that's no limit and does its best to make the rest of the game as no limit as possible while still obeying the letter of the law.