Definition of split
A split is when a pool is separated. A pot can be split for two reasons: when two players have the same hand at the slaughter or when playing a "high-low" variant, i.e. a variant in which you often play for two halves of the pot, one half you win when you make the best "high" and one half you win when you make the best "low". In variations of high only, if 2 or more players have the same hand, the pot is split equally. A split-pot can also occur when the board gives the best hand to everyone (for example, if a board gives T-J-Q-K-A and there is no possibility of a flush).
What if the jackpot is not divisible by 2?
Let's say you're playing one-on-one with a player. You arrive at the slaughter on a 2-2-5-5-7 board and both of you have AK. Then there are split pot. But the pot is $10.11, a number that cannot be divided by two (actually yes, but $0.01 is the smallest unit of money). What do we do now? We distribute 5.05 to each player and the excess ($0.01) goes to the player who was out of position postflop.