Poker is a card game with a wide range of strategy. While the outcome of any individual hand may involve some element of luck, the long-run expectations of players are determined by actions chosen on the basis of probability, psychology, and game theory. Some of these actions are bluffs designed to mislead other players, but most involve betting in order to maximize the chances of winning.
The game begins with 2 cards being dealt face down to each player and then a round of betting starts. The first 2 bets are forced bets which come from the players to the left of the dealer, these are called antes or blinds and they are placed into the pot before any other betting starts.
After the flop is dealt there is another round of betting. At this point players can choose to check, fold, raise, or call. When you are holding a strong hand like a pair of kings or queens and the board has tons of high cards you should raise to price out all the worse hands. If you are holding a weaker hand you should fold and wait for your next opportunity.
As you play more and observe other players you will be able to read their tells better, this will allow you to make quicker decisions. If you see a player making a lot of calls but then suddenly raising it could be a sign that they are holding something special!