Poker is a card game in which players place an initial amount of money into the pot before being dealt two cards. Depending on the rules of the game, each player may call that bet by placing the same amount into the pot, raise it or drop out of the betting interval completely (again, this depends on the rules).
A poker hand is made up of one or more cards of equal rank. The highest-ranking hand wins the pot at the end of each betting round. The pot is the total amount of bets placed by all active players in the current betting interval.
As a rule, top players fast-play their strong value hands to build the pot and chase off other players who are waiting for a draw that could beat them. This is a much more profitable strategy than calling every bet and losing money on later streets.
You can read books about poker strategies, but it’s also important to study your own play and take detailed notes so you can find a unique approach that works best for you. Some players even discuss their hands and playing styles with friends for a more objective look at their strengths and weaknesses.
As you play more and more poker, the math will begin to ingrain itself in your brain naturally, so don’t worry about it too much. Over time, you’ll start to have a natural intuition for things like frequencies and EV estimations.