The Castanets are an instrument in the percussion family. One pair consists of two pieces of hard wood in the shape of a shell that are hinged together by a string. Their name comes from the Spanish word castañuelas, which means chestnut (which they look a bit like).
They are held in the hand, and when the wood pieces strike each other, they produce a clicking sound that is often associated with Spanish dances. They can be used to create rhythmic accents, or they can be played very fast, which adds color and excitement to the music!