A flush is a poker hand that consists of five cards of matching suits, whether all five cards are hearts, spades, clubs, or diamonds. The cards don’t have to be in any particular order.
A flush is the fifth strongest hand in poker, coming right behind a full house and ahead of a straight.
For example, a flush can be a 5s 7s 8s 9s Js or an Ac 2c 5c 6c 10c hand. If the five cards are also in consecutive order, then it’s a straight flush.