A split pot is when two or more players share the pot at the end of a hand. This happens if several players put in the same amount of money into the pot and end up with the exact same hand on a showdown.
For example, there’s only you and one more player left in the hand. As the board runs out A, K, Q, 7, 3, both of you turn your cards to reveal a J, 10 off-suit. Since both of you have an equally strong straight, you split the pot.
Another example could be that no player has made a hand, and the cards on the community board are the strongest possible hand, so the pot is split between the players.