A piano is a keyboard instrument, which is widely used in western music for solo performance, chamber music, and accompaniment, and also as a convenient aid to composing and rehearsal.
The piano produces sound by striking steel strings with felt hammers. These vibrations are transmitted through the bridges to the soundboard.
The word piano is a shortened form of the word "pianoforte", which is seldom used except in formal language. It is derived from the original Italian name for the instrument, clavicembalo col piano e forte--literally harpsichord with soft and loud. This refers to the ability of the piano to produce notes at different volumes depending on how hard its keys are pressed.
As a keyboard stringed instrument, the piano is similar to the clavichord and harpsichord. The three instruments differ in the mechanism of sound production. In a harpsichord, strings are plucked by quills or something similar. In the clavichord, strings are struck by tangents which remain in contact with the string. In a piano, the strings are struck by hammers which immediately rebound, leaving the string to vibrate freely.