Poker is a card game in which players place bets against each other in a communal pot. While the outcome of any particular hand significantly involves chance, the long-run expectations of individual players are determined by their actions chosen on the basis of probability, psychology, and game theory.
After a forced bet, such as the ante or blind bet, the dealer shuffles and deals five cards to each player in turn. Each player may then choose to call, raise or fold his cards. If he raises, the player to his right must either call or fold. Players may also discard cards and take new ones as they wish. The best hand wins the pot.
Playing a winning strategy in poker requires quick instincts and an ability to adapt to the actions of other players. Watching experienced players and thinking about how you would react in their situation is one of the best ways to develop these skills.
A good starting point is to read some books on poker strategy. Look for books that were published recently, as the game has evolved dramatically over the past 40+ years.
Another way to improve is to talk about hands with winning players. Find players who are winning at your stake level and start a group chat or meet weekly to discuss difficult spots you have faced. This will help you understand different strategies and see how other winning players think about these situations.