As shown in the poker hand rankings chart, the order of poker rankings (from the highest to the lowest) is: Royal Flush, Straight Flush, Four-of-a-Kind, Full House, Flush, Straight, Three-of-a-Kind, Two Pair, One Pair, High Card.
A flush is a hand that contains five cards all of the same suit, not all of sequential rank, such as K&c 10&c 7&c 6&c 4&c (a "king-high flush" or a "king-ten-high flush"). It ranks below a full house and above a straight. Under ace-to-five low rules, flushes are not possible (so J&e 8&e 4&e 3&e 2&e is a jack-high hand).