According to pianoeducation.org, the piano is a hybrid, a combination of two instrument families: strings and percussion. The strings give the piano its musical tones, but those tones are produced by hammers striking the strings and causing vibrations.
The piano was invented in about 1700 by Italian harpsichord maker Bartolomeo Cristofori. On the harpsichord, sounds are created by plucking the string when a key is pressed. Cristofori, looking for a keyboard instrument that could generate a more assertive sound with variable volume, fashioned a harpsichord with small hammers that hit the strings instead of plucking them. The mechanism allowed the instrument to produce a sound that could become louder or softer with the player's touch. The piano was first called the pianoforte, meaning soft-loud.