These are the Hand Rankings in Poker. From highest to lowest.
A Straight Flush - is the highest possible hand that can be called in a game of Poker. If the highest card is an Ace, followed by K, Q, J, 10, it is called a Royal Flush.
Four of a Kind - Four of a Kind is when you have been dealt four cards with the same value, for instance, 4 Kings or 4 Eights. Its a very high ranking hand. If two players both have Four of a Kind, then the game is won by the player with the higher valued Four of a Kind. Example, K, K, K, K, X would beat 8, 8, 8, 8, X.
Full House - A Full House is where the player has been dealt 3 cards of the same value and a pair. Example, Q, Q, Q, 4, 4. Should another player also have identical poker card values, ie. another Full House, then the winner would be the person who's triple had the highest value. Example, K, K, K, 8, 8 would beat 5, 5, 5, Q, Q.
Flush - A flush is where all of the cards dealt to the player are of the same suit. They can be of any card values. Example, 2, 6, 9, J, K of Clubs. When two players tie, again the highest valued card of either hand determines the winner. (See High Card below.)
Straight - A Straight is where the 5 cards value is in a running order but are made up of different suits. Example; 3, 4, 5, 6, 7 but varying suits. Where two Straights tie, the highest value Straight is ranked higher and wins. If both Straights have the same value highest card, then the pot is evenly split between both players.
Three of a Kind - If a hand holds 3 cards of the same value, then it is said to hold Three of a Kind. Example, K, K, K, 4, 8. If two players both have Three of a Kind, again the highest value 3 cards win. In community card games where players have the same three of a kind, the highest side card, and if necessary, the second-highest side card wins.
Two Pairs - Two Pairs is when the player has been dealt 2 sets of 2 cards of the same value (this may seem obvious.) Again, if two players have Two Pairs, then the highest value pair wins. In a draw situation, the highest 5th card would be the decider.
One Pair - One pair dealt with 3 other differing value cards. When two players both have a Pair, then again the highest ranked pair wins. The High Card rule is the decider, yet again, in a tie situation.
High Card - When all cards in the poker hand are of different values and suits do not follow any of the above sets of rules, then the highest value card in the hand is how the value of the hand against the other players is ranked. In a tie situation where two players have the same poker hand value using their respective High Cards and they are both the same value then these cond highest value card is used, and so on. As mentioned above, the High Card value is used to determine the winner, in tie situations with Two Pairs, Three and Four or a Kind.
There are a few variations of poker in which low ranking hands have a higher value, but for all practical purposes these rankings are what you need to know. Most games of poker revolve around making the best possible five card hand. The order (or value) of these hands is based upon the mathematical probability of being dealt each hand. Ace is considered either high or low depending on the hand all other cards are worth their face value, Queen is better than a Jack but not as good as a King, etc.