Counter Strike is a FPS Game (First Person Shooter) Where your goal is to kill the enemy team and win the game. There are different gamemodes like Ranked which is a 5v5 and you have to kill the entire enemy team to win 1 round and you neeed to win 16 of those rounds. There is other gamemodes like FFA (Free for all) Which you have to kill the most people in the game
There is different servers people make that you can play. One of these is called "Surf" surf is where you have to hold out your knife on a big block where you essentially surf on the block and jump to other blocks (Kind of like parkour).
There is also a Battle Royale which there is a certain amount of players and you spawn in a random position, from there you have to gather loot to be able to kill the other players and be the last one standing.