Poker is a card game of chance that involves betting and raising bets until one player has the best five-card hand. Players start by placing an initial bet (the amount varies by game). Once all players have placed their bets, the highest hand wins the pot.
Players may bet in any order they choose (again, the amount varies by game). They can put out chips equal to the big blind (call), raise by at least the size of the last raise (raise), or push their cards face down without putting any chips in (fold).
If you have a strong poker hand, then you should always bet it. This will build the pot and force out players with weak hands. You can also bluff, although this is usually only effective when your opponent knows that you are holding a good hand.
It is important to study your opponents. Top players will often work out the range of cards that they could have and then work out how likely it is that their opponent has a hand that beats theirs. This will help them to make better decisions at the table.