What do pedals on a piano do?

The three pedals that have become more or less standard on the modern piano are the following. From left to right: una corda, sostenuto and damper. The damper pedal (also the sustaining pedal or loud pedal) is the most frequently used. It is placed as the rightmost pedal in the group. Every string on the piano, except the top two octaves, is equipped with a damper, which is a padded device that prevents the string from vibrating. The damper is raised off the string whenever the key for that note is pressed. When the damper pedal is pressed, all the dampers on the piano are lifted at once, so that every string can vibrate. This serves two purposes. First, it assists the pianist in producing a legato (playing smoothly connected notes) in passages where no fingering is available to make this otherwise possible. Second, raising the damper pedal causes all the strings to vibrate sympathetically with whichever notes are being played, which greatly enriches the piano's tone. The una corda pedal (also the soft pedal) is placed leftmost in the row of pedals. On a grand piano this pedal shifts the whole action to one side, slightly to the right, so that hammers that normally strike all three of the strings for a note strike only two of them. This softens the note and modifies its tone quality. On many upright pianos, the pedal operates a mechanism which moves the hammers' resting position closer to the strings. This reduces the volume as the hammers have less distance to travel, but this does not change tone quality in the way the una corda pedal does on a grand piano. However when this pedal is depressed on the vertical, it changes the action creating what is called lost motion, that is the jack is now further from the hammer butt, and now has to travel further to engage the hammer. This lost motion changes the touch and feel of the playing action, and as a result many pianists never use the soft pedal on a vertical. Since the grand piano soft pedal simply shifts the action sideways, it does not change the touch and feel of the action, another advantage grand pianos have over vertical pianos. The sostenuto pedal (also the middle pedal) keeps raised any damper that was raised at the moment the pedal is depressed. This makes it possible to sustain some notes (by depressing the sostenuto pedal before notes to be sustained are released) while the player's hands are free to play other notes. This can be useful for musical passages with pedal points and other tricky or impossible situations. The sostenuto pedal was the last of the three pedals to be added to the standard piano, and to this day, many pianos are not equipped with a sostenuto pedal. Almost all modern grand pianos have a sostenuto pedal, while nearly all upright pianos do not. Some upright pianos have a celeste pedal (practice pedal) in place of the sostenuto. This pedal, which can usually be locked in place by depressing it and pushing it to one side, drops a strip of felt between the hammers and the strings so that all the notes are greatly muted-- a handy feature for those who wish to practice without disturbing everyone else in the vicinity. http://en.wikipedia.org/wiki/Piano#Pedals

Thank you to Janet Yun