A conker is the seed of the horse chestnut tree, known for its shiny, brown appearance. These seeds fall from the tree in autumn and are often collected by children for a traditional game. The game involves two players taking turns to strike each other's conkers, aiming to break the opponent's conker while keeping their own intact. Conkers are typically about the size of a marble and have a hard outer shell. While they are not edible for humans, they are sometimes used in crafts or as natural decorations. The game of conkers is especially popular in the United Kingdom and has been played for generations.