Poker is a card game in which players bet on the outcome of hands. Each player must place a number of chips representing money into the pot in turn before seeing their hand. These initial forced bets create the pot and encourage competition. In the long run, however, money is only placed into a hand if a player believes it has positive expected value. This decision is based on a combination of probability, psychology and game theory.
A successful poker player must be able to read his opponents. This is done through studying their actions and using information available from the table. This information includes how much of their stack is left (pot size), the size of their raises (a bigger raise means that they have a better hand than yours and should be called) and their general tendencies.
Another important skill is understanding ranges. While newer players try to put their opponent on a specific hand, more experienced players work out the entire selection of hands that the opponent could have and calculate how likely it is that these hands beat theirs.
Knowing the order of poker hands is also important. A royal flush is five cards of the same suit in sequence. A straight is five cards of consecutive rank, but from different suits. Three of a kind is three cards of the same rank and two unmatched cards. Two pair is two matching cards and one unmatched card.