Percussion instruments are played by being struck or shaken. The two major categories are membranophones, which add timbre to the sound of being struck, such as drums, and idiophones, which sound of themselves, such as the triangle.
Most percussion instruments have a distinct tone. Even drums are tuned. However, a distinction is usually made based on whether the instrument can play a definite pitch or not.
The timpani, xylophone, vibraphone, triangle, tubular bells, glockenspiel, all play a definite pitch. The snare drum, bass drum, cymbal, maracas, claves, wood block do not.