Winning poker hands are determined by rank. If two or more hands are in the same category, the best hand is determined by the rank of cards. For instance, two players might hold Four-of-a-kind, but four Jacks beats four sixes.
Rank of Cards (in descending order): ACE, KING, QUEEN, JACK, 10, 9, 8, 7, 6, 5, 4, 3, 2.

All suits are of equal rank in poker.

1. STRAIGHT FLUSH.
Sometimes a ROYAL FLUSH (the best Straight Flush) is considered to be a separate category. A Straight Flush is five cards in consecutive order all of the same suit.
A Royal Flush is A-K-Q-J-10 of the same suit. With any Straight, including a Straight Flush, the Ace can be used low. Therefore, 5-4-3-2-A of the same suit is a Straight Flush (but it's only 5-high and would lose to 6-5-4-3-2 of the same suit, even though the first hand contains an Ace.) The higher high cards determine the relative rating of Straight Flushes.

2. FOUR-OF-KIND.
Such as 4-4-4-4-K. The relative rating, if two or more hands vie in this category, is determined by the strength of the four cards of the same rank, not by the odd card.

3. FULL HOUSE.
Three-of-a-Kind with a pair. The relative ratings are determined by the rank of the Three-of-a-Kind, not the pair.

4. FLUSH.
Five cards of the same suit. If there are two (or more) flushes tied, the higher card wins. If this is a tie, then the next card determines, and so on. Therefore, A-K-9-4-3 of Hearts beats A-K-8-7-6 of Spades.

5. STRAIGHT.
If there are two (or more) flushes tied, the higher card wins. If this is a tie, then the next card determines, and so on. Therefore, A-K-9-4-3 of Hearts beats A-K-8-7-6 of Spades.

6. THREE-OF-A-KIND.
If more than one player holds Three-of-a-Kind, the rank of the three matched cards determines the winner.

7. TWO PAIR.
The highest Pair determines the winner if two players (or more) have Two Pair. If both high Pairs are the same, then the better remaining pair determines the winner. For instance, 9-9-7-7-4 beats 9-9-6-6-A. If both Pairs tie, then the unpaired card determines the winner. Therefore, 8-8-4-4-7 beats 8-8-4-4-5.

8. ONE PAIR.
If tied, the higher Pair wins. If both Pairs are the same, the highest remaining card wins down to the last card, if necessary. For instance, A-A-K-4-2 beats A-A-Q-J-10 and K-K-9-8-3 beats K-K-9-8-2.

9. NO PAIR.
The winner is determined by rank of cards only. A-7-6-4-3 beats K-Q-J-10-7 and Q-8-7-6-5 beats Q-8-7-6-4.

There will occasionally be ties in poker. When this happens, the pot is divided evenly among the winners.