"What's GNU?" is a family game by ThinkFun that involves learning and spelling words. With a minimum of 2 players, this educational game is suitable for children ages 5 and up, as well as older teenagers and adults. Players take turns guessing 3-letter words based on clues given by the other players. The game helps improve vocabulary and spelling skills in a fun and interactive way, making it a great option for both solo and multiplayer play.