Under high rules, an ace can rank either high (as in A♥ K♥ Q♥ J♥ 10♥, an ace-high straight flush) or low (as in 5♦ 4♦ 3♦ 2♦ A♦, a five-high straight flush), but cannot simultaneously rank both high and low (so Q♣ K♣ A♣ 2♣ 3♣ is an ace-high flush). With this in mind, there are 10 five-card sequences of consecutive dominations. Since an ace can be 'high' or 'low', it can be thought of as 14 or 1.
One can think of J as 11, Q as 12, and K as 13. The most usual kind of poker is “high poker” where aces are always high, except the ace can optionally be low for the purpose of making a straight (that is, A-2-3-4-5 is a straight, and so is 10-J-Q-K-A).
