Poker is a card game that takes place at a table with a dealer. The cards are dealt to each player face down and then there is a round of betting. The best hand wins the pot. There are a number of variations to this game including stud, draw and community cards.
One of the keys to success in poker is not falling prey to emotion. There are three emotions that can kill a poker game: defiance, hope and fear. Defiance is the desire to hold your own against players who are better than you, but it will only end up costing you money. Hope is what keeps you in a bad hand long after it should have been folded and can lead to costly bluffs. Fear is the fear that you will be called by someone with a good hand, and it can also ruin your chances of winning.
Another key is to be able to read your opponent(s). This is a combination of understanding how each type of hand plays and knowing their tendencies. A good way to learn this is by studying poker numbers, like frequencies and EV estimation. These numbers will become ingrained in your poker brain over time and will help you make better decisions during hands.