Explain to me what is the game Minecraft about?

It's not about anything, its a game you make your own - create your own world, make creatures if you want, make it a farm, make it a zombie game, explore other worlds and so on
you use materials you get from the environment such as bricks and trees you mine or cut down, you find items that are used to make the living animals, you decide what you want to do

It's not a game for everyone but it is a game most people can find some fun with, check out videos on youtube of the console versions ( which are pretty limited vs the pc game but still not bad for a smaller version ) , see if you think you'd like it and if you don't then that's fine, just get another game

Well, it's an adventure game. You can hang out with friends on multiplayer servers, build, raise animals, kill creatures that only appear in the night, create armor and weapons, go to a different dimension, and stuff like that. It's pretty fun.

Yeah google it or go to youtube you build stuff outta blocks and survive.