Poker is a card game in which each player bets his or her chips (representing money, for which the game is almost invariably played) according to the rules of the particular poker variant being used. The amount of money placed into the pot in any given round is determined by a combination of chance and decisions made on the basis of probability, psychology, and game theory. While some initial forced bets are made, the majority of money placed into a pot is voluntarily placed by players on the basis of expected value calculations.
Each poker player has three options when he or she has been dealt cards: Call, raise, or fold. When a player calls, he or she places the same number of chips into the pot as the player before him or her. The player may also choose to raise the total amount that is being bet by placing chips into the pot in an increment greater than the previous bet.
A player who has good cards and feels a strong chance of winning the hand should always bet. This will force weaker hands out of the pot and lead to a higher winning percentage. However, it is sometimes smarter to fold a bad hand rather than continue betting money at it. Often, this will save you more than it costs in the long run.
It is important to realize that poker is a game of skill, not luck. Even million dollar winners started out at the bottom of their field, and they generally only play against players who are better than them. That is why it is important to start out playing at the lowest stakes levels, and only move up to larger stakes when you have improved your skills significantly.