It's a multiplayer game which starts with a given number of tokens. Players take turns to pick 1 or 2 tokens. You have to strategically pick the tokens so that you pick the last token and win the game.
This is great for kids, as it helps to concretely and actively build the ideas of counting, addition, subtraction, finally leading to strategic thinking.
Great for people of all ages as it allows you to think about winning strategies in multiple scenarios.