The right pedal is called the sustain or damper pedal. Its function is to lift all the dampers off the strings so that any notes played thereafter will sustain (continue to sound), and all other notes will ring sympathetically. The left pedal is called the soft pedal (vertical) or una corda pedal (grand). Its function is to reduce the sound volume somewhat by moving the hammers closer to the strings (vertical), or by shifting the keyboard so that only two out of each group of three strings is struck by the hammers (grand).
The center pedal has one of several different functions. In most grands and a few high-quality verticals, it acts as a sostenuto pedal, selectively sustaining only those notes whose keys are down when the pedal is depressed. This feature is useful only in a few pieces of classical music. In most verticals, the center pedal either lowers a strip of muting cloth between the hammers and strings, drastically reducing the sound volume, or operates as a sustain pedal for the bass notes only.