Poker is a card game in which players place bets into a pot in the center of the table. The player with the highest ranked hand wins the pot.
Each player must ante something (amount varies by game; ours is a nickel) and then they are dealt cards. Once the betting gets around to you (it always starts to the left of the dealer) you can fold, call or raise.
Once the betting is complete on the flop the dealer puts down three more cards that everyone can use. This is called the turn. Then the river is the fifth and final community card. After this round of betting the dealer announces which hands are winning and pushes the pot of chips to the winner.
As you learn to play poker the more you will understand the importance of position. It has a huge impact on your starting hand strategy. Players in early positions like the SB and BB risk more money because they have less information on their opponents than the players behind them. In general, the later your position is, the better. The reason is because the people that act after you can see your entire range of possible hands. This allows them to make more informed decisions than you can. They can also raise your bets without you knowing it. This is a huge advantage. It is also why it is important to learn the game by watching others play and analyzing their behavior.