Poker is a card game in which players place bets into the middle (the pot) to compete for a winning hand. Unlike most other casino games, poker involves no forced bets, and money is only placed into the pot when it has positive expected value. Players make decisions on the basis of probability, psychology, and game theory.
To begin the game all players must ante something into the pot, this amount varies by poker game and table. After that players are dealt cards and the betting begins. Typically players bet in clockwise order, and raise and/or fold their hands as they see fit.
After the first betting round is complete the dealer will deal a third card on the table that all players can use, this is called the flop. Then another betting round takes place and once that is over the fourth card will be revealed, this is known as the turn.
You should always look at the cards on the table to figure out what other players may have. It is very difficult to know exactly what other players have in their hands but you can usually narrow down the possibilities. For example, if someone checks after the flop and you have pocket kings it is safe to assume that they have a high kicker, which will likely win the showdown. You can also use the board to figure out what other players may have by looking at the type of cards that are on it.