Poker is a card game that involves chance, but it also relies on skill and psychology. When players place money into the pot, it is a voluntary action and they do it because they either think their bet will have positive expected value or they are trying to bluff other players for various strategic reasons.
Once the players have all called at least the amount of the highest raise (or folded) a new round of betting begins. This is known as the flop.
The dealer shuffles the cards and then deals them out to each player, one at a time. The first player to act raises and then the rest of the players may call, fold, or raise again. The raised amounts are placed into the pot and a showdown ensues.
A pair of matching cards, either high or low, beats a single card, 2 pairs beat 3 of a kind and 4 of a kind beats 5 of a kind. Straights are five consecutive cards of the same rank (such as 4-5-6-7-8) and can be either high or low. If two straights tie, the higher straight wins.
The most important thing to remember is that you have to be able to read your opponents. A lot of people have an overarching ability to read others, but you need to get more granular and learn to pick up on things like mood shifts, hand movements, and tells.