Please who knows what Pokémon Go is?

I've been seeing memes about Pokémon Go on Instagram, Palmchat, Twitter, Facebook, etc... But I don't know what it is. Even M.I. Abaga plays it!

Heard it is a game and a lot of people in the world are currently obsessed with it, but Rihanna told her fans that she does not want them playing the game at her concert. Why

Please does anyone here play the game? I want to download it, but it must be worth my data o! LoL!