Poker is a card game that involves betting and the raising of hands. The player with the highest hand at the showdown wins the pot which is all of the money that has been bet during the current hand. Players place money into the pot voluntarily, choosing to either call, raise or fold depending on a combination of probability, psychology and game theory.
There are a lot of things to learn in poker but one of the most important is the concept of ranges. A good range allows you to work out the selection of possible cards that your opponent could have and to determine the odds of a hand beating yours.
Good pocket pairs (pocket kings, for instance) are ruined by a flop of jacks or higher and bad suited connectors (like 7
If you want to be a winning poker player you need to understand the principles of the game and apply them in a disciplined way. This requires a level of mental commitment that few can maintain, especially if they are playing for a living. It is a highly psychological game that can quickly derail a good player when they are frustrated or tired and are tempted to make a poor call or ill-advised bluff.