When players have the same five-card hand, or during games like high-low where certain hands can take parts of the pot, then the spot has to be split: divided into halves or even smaller parts so different players can take their winnings. At casinos, dealers do this for you, but at home games, you'll need to manage the pots, the math, and the winnings yourself.
Pots get split in a variety of situations:
On the surface, splitting pots is easy enough: simply take the pot, split it evenly, and each player takes their winnings.
This is especially easy when two players have the same five-card hand: each takes half. If it's three or four or more players all with the same hand, divide the pot by the number of players, and each player collects their winnings.
But things can get tricky fast.
In high-low games, the easiest split pot is when one player wins the high and the other wins the low. Here, you simply divide by two and each player collects their winnings. A player with the best high and the best low hand "scoops" the whole thing.
But, especially in games like Omaha High-Low, when lots of players might all have the same low or the same high, the pot needs to be split along more complicated lines.
For instance, more than one player might all have the same low hand--this is easy enough if a board contains lots of low cards. On the other hand, multiple players might share the same high--for example, they are all able to make the same straight.
In these cases, the easiest way to manage the pot is to first split it in two: one high pot and one low pot. Then, the players who share the same high divvy up the high pot, and the players with the same low divvy up the low pot. (This is the same way you would divvy up a pot in a game like Chicago: split the pot in two, with one half going to the player with the high spade in the hole, and the other half going to the player with the best five-card hand--and yes, sometimes those halves get scooped by the same player!)
The most common example of this is quartering: two players have the same low hand, but one has a better high hand. So they split the low, and one player takes the high, so that one player gets 75% of the whole pot and the other gets 25%--a quarter. But it's not uncommon for three or more players to play for the same high or low, so players might get one sixth or one eighth or an even smaller fraction of the pot, while one player ends up take two-thirds of five eights for themselves.
When one player is all in, they can win the main pot: the pot that every active player can theoretically win. But other players can continue betting amongst each other by placing their chips into a side pot: a pot that only some active players can win. And yes, sometimes the side pots can get even bigger than the main one!
On the surface, side pots are relatively simple: the main pot usually gets stacked near the player who is all in, and the other two players can bet into the side pot. But, when multiple players are all in, there might be more than one side pot: for instance, a player is blinded all in, another player goes all in on the flop, and other players continue betting through the river and turn. Imagine what can happen if there are three or four or more players all in at the same time, with side pots stacked all around the table, while two big stacks keep betting into one another--complicated enough at a Texas Hold'Em table, and even more so at a High-Low game, where all those pots could get split up even more!
In these cases, the key is remembering who can win each pot. At casinos, this is simple enough, since the dealer sorts out each pot. But at home games, it's crucial to remember who can win each pot: every player can win the main pot, including the player who went all in first; then the next side pot can be won by everyone who could match the next all-in bet; and so on and so on. If it sounds complicated, don't be afraid to take extra steps to sort it out--if you play a lot of Omaha High-Low, you might consider keeping a pad and paper at the table!
Inevitably, there will be a pot that can't be split evenly: a 5-cent chip that can't be broken down, or an even number of players will try to split a pot with an odd number of chips in it.
In these cases, it's always useful to be able to make change: break down one of the chips into smaller denominations so that the chips can be divvied out as evenly as possible. At casinos, the dealer will handle this. At home games, players can work it out with one another by making change with one another or with the bank.
But what to do with an extra chip that can't be divided evenly? Different games have different rules. Some leave it in the pot for the next hand, some give it to the player closest to the big blind. Others pick a high card, others let the dealer take it. Always know the rules of the home game you're playing in.