Side Pots

When stacks differ, one pot becomes two.

The flop. Before the flop, you, Darius and Zofia each put in 4. Layla folded her small blind of 1. Pot: 13.
Zofia goes all in. Zofia acts first and pushes all 56 chips in.
You call. You have more than 56, so you can match it all. You call 56.
Darius calls short. Darius has only 16. He calls all in for 16. He can still win, but only the part of the pot he could match.
The main pot. The dealer builds the main pot first: the 13 already there, plus 16 from each of you three. 61 chips. All three can win it.
The side pot. The other 40 from you and 40 from Zofia go in a side pot: 80 chips. Darius did not match that, so he cannot win it.
Run it out. Zofia is all in, and Darius is too. No one is left to bet against you, so the turn and river come out.
Showdown. Darius: three queens. You: a pair of queens with an ace. Zofia: a pair of eights.
Who wins what?. Tap the player who wins the side pot. Darius cannot win the side pot. Of you and Zofia, your queens beat her eights.
Paid out. Darius takes the main pot, 61. You take the side pot, 80. You lost to Darius and still came out ahead.

Play money only. Room rules differ, so ask the dealer when in doubt.