what is minecraft

I'm a 40-year-old man and I'm about to play Minecraft for the first time. I'm doing it for you, for me, for all of us that have no rational idea of what it is, what it does or what it means. Is it Adolf Hitler's second, more 'downtime' book? Or some trending subterranean hobby that they're all psyched about on the QVC channel? From the look of the screen in front of me, no.