The term “outs” in Texas hold’em refers to the number of cards that will help you make the best hand when drawing. Learning how to calculate outs is often among the first type of “poker math” absorbed by new hold’em players. Whether by trial and error through playing or by reading through strategy articles or books, players soon commit to memory the outs needed for commonly faced draws.
For example, on the turn the board shows and you hold . Knowing there are 13 hearts in the deck and being able to see four of them — two on the board, and two in your hand — it’s easy enough to figure out there are nine more hearts potentially left to make your heart flush and (presumably) what figures to be the best hand.