Side pots help keep a game going
Life is not fair. Sometimes, bad things happen to good people, and bad people get away with doing bad things. That life isn't fair is one thing that a lot of people realize early on in life and must soon learn to accept if only to know how to deal with it. Thankfully, man also has it in him to level the playing field a bit, and that is why we have laws and the justice system, scholarship programs, and rehabilitation centers, among others.
The same has also been applied in the world of poker. Poker attracts all kinds of players, and not everyone will come to the table with equal resources. True, being a table stakes game, players can only wager what they have in front of them when the deal begins but neither should certain plays be forced by whoever has the most. Otherwise, at a table of players with equal skills, it may come out to making sure that you always have more than the others.
Thus, the concept of side pots. This is obviously relevant to a game with more than two players involved. From the name itself, side pots are made on top of the main pot to accommodate the wagers of the other players once one of them has gone all in.
To illustrate this better, let us take a look at a table with three players, A, B and C, with $20, $40 and $60 respectively. Several rounds have gone by and the main pot now contains $60. Player C wagers for $30 which is more than what Player A has (at $20).In this case, A does not have to be bet out of hand because he cannot meet the $30. Instead, he may go all in, that is, wager his remaining $20, or fold. If A decides to go all in, then Player B himself call, raise or fold. However, should B decide to call, he must call the original wager of $30 rather than A's $20. Once B decides to call, that is when a side pot is created.
With the above example, the main pot is now $120, from the original $60 and the $20 from each player. However, since both B and C have $10 extra each from their $30 bets, a side pot of $20 is then created. This way, all three players are still in on the game. It is important to remember that the side pot may only be won by those who contributed to it, thus A above could win the main but not the side pot. Only Players B and C can do so.