A piano is a musical instrument that produces sound by striking strings with hammers when keys are pressed. It typically has 88 keys, which include both white and black keys, allowing for a wide range of musical notes. Pianos can be classified into two main types: grand pianos, which have a horizontal design, and upright pianos, which are more compact and vertical. Pianos are commonly used in various music genres, including classical, jazz, and pop. They can be played solo or as part of an ensemble. Many musicians learn to play the piano as it serves as a foundation for understanding music theory and composition.