FO4 stands for Fallout 4, which is a video game where you get to explore a big open world after a nuclear war.
You get to create a character and make choices that affect what happens in the game, like whether you want to be a good or bad person.
You have to find things like food, water, and shelter to survive in the game. Along the way, you'll meet all sorts of different people and creatures, some of which will want to hurt you.
You get to use different weapons and special powers to fight back against your enemies. You can also build your own houses and settlements to keep yourself safe and comfortable.
Overall, FO4 is a really fun game that allows you to explore a post-apocalyptic world while making choices that determine your fate.