Poker is a game of betting over a series of rounds. The player with the best five-card hand wins the pot. There are many different variants of the game, but they all share some basic aspects. In each round you bet either by calling or raising. You can also fold when you believe you cannot win. The dealer deals the cards and then begins the betting process.
In most games you will bet the same amount each round. This is called the betting interval. Depending on the game, this can be once or twice per deal. After the first betting interval is complete the dealer puts three cards face up on the board. These are community cards that everyone can use for their hand. Then the dealer will put a fourth card on the table that anyone can call or fold.
Beginners should start out tight, only playing the top 20% of hands in a six-player game or 15% of hands in a ten-player game. You can find pre-flop range charts online that will help you determine this. You should also be watching your opponents closely and reading tells.
There are some players who have a very specific style of play and they can make good money because other players will always call their raises. However, most beginners will lose some money at the beginning. The key is not to let this discourage you. Keep improving your game and learn from your mistakes. Watch videos of Phil Ivey playing bad beats and notice how he never gets upset.