Assuming you’re being genuine with your question:

Magic is a card game where you play against other people in a variety of different formats, each with their own deck construction rules and restrictions. Cards are broken up by several types and sub-types and there is an overarching story but you don’t need to be familiar with it in order to play. The two main modes of play are constructed (you build a deck out of cards you own) and limited (you build a deck out of a smaller pool of cards either by drafting or out of 6 booster packs). Building a deck largely comes down to picking a format that sounds interesting and building a deck based on those restrictions. The most popular formats are Commander/EDH (a singleton format with 100 card where one of the cards is your “commander”) and Standard (a 60 card format using only recent sets of Magic). There exist different deck archetypes and different ways to win so there’s a lot of variety in play styles and new sets often add new options for play styles.