The first step to becoming a successful poker player is to know the ranking of poker hands - what beats what!
It seems tricky, at first, but it becomes second nature after just a bit of practice. And it is well worth learning, now, because you don't want to find out middle of an online poker tournament, just when you think you've won a big pot, that your straight does not hold up against that flush. Let's avoid that, shall we!
Also if you are beginner, try you hand at lot of free poker sites before finally deciding to take the plunge. For example, pokerstars let you play in so-called "play money" games that does not involve real money. Or if you make a deposit, they will give you a 100% bonus match up as a new player.
The winner of a poker hand is determined by the best five-card combination. In some games like Texas Holdem, where each player in the hand has seven cards (two of his own and another five community cards), the strength of his/her hand is determined by the top FIVE cards out of those seven. Here are the rankings of hands from lowest to highest:
High Card: Five card hands without any pairs. (A-10-9-4-3) This hand is A-high; beats K-high (K-J-5-4-2), which beats Q-high, etc.
One Pair: AA, KK, QQ: This (A-A-K-10-4) is a pair of aces; beats KK's (K-K-10-9-8) which beats QQ's, etc.
Two Pair: KK and JJ, 88 and 99 (K-K-J-J-6) (8-8-9-9-Q). The strength of the two pair is determined by the highest pair. Because AA is higher than KK, a hand like AA and 33's BEATS KK and QQ's.
Three of a Kind: The same three cards and two different cards. Trip fives; trip nines (5-5-5-6-Q) (9-9-9-4-2)
Straight: Five connecting, consecutive cards. (2-3-4-5-6) (9-10-J-Q-K) The higher the cards, the higher the straight. Ace counts for both low straights A-2-3-4-5, and the highest "Broadway" straight 10-J-Q-K-A.
Flush: Any five cards of the same suit - spades, hearts, diamonds, clubs. In the rare event that two players hold the same hand in different suits, the winner is determined by the highest suit. The rank of the suits, from highest to lowest, are Spades, Hearts, Diamonds, Clubs.
Full House: Three of a kind AND a pair (9-9-9-J-J) (K-K-K-3-3) These hands are nines FULL of JJ's, Kings full of threes. This hand is also called a boat.
Four of a kind: Four of the same card (3-3-3-3-K) ... these are also called QUADS ... one could pronounce this hand as quad-three's.
Straight-flush: Five connecting cards AND suited cards, such as 6-7-8-9-10, all Diamonds! Or 8-9-10-J-Q, all spades!
Royal Flush: the top five connecting AND suited cards: 10-J-Q-K-A, all of the SAME SUIT! This is the rarest hand of them all.
Do not get intimidated if you have never played poker. You will very quickly memorize the hand rankings with a little of practice. Make sure to play at a reputable poker site such as pokerstars.