When talking about audio, the terms
balance and
pan are often used
interchangeably, particularly within music playing software such as
Winamp, but there is a significant difference between the two.
Balance
A typical home stereo has a balance slider on the front. The idea is to set the balance control such that you hear equal volume from each speaker. This often isn't necessary, but if you sit right next to one speaker and far away from another, it makes sense to use it. To achieve this, the volume of each channel is raised or lowered accordingly, but the mix of left and right in each speaker is unchanged.
If we take the example of some music recorded with a piano all the way to the right in the stereo field and a guitar all the way to the left...
-----|----- BALANCE CENTRED
right speaker: piano
left speaker: guitar
---------|- BALANCE 90% RIGHT
right speaker: loud piano
left speaker: quiet guitar
-|--------- BALANCE 90% LEFT
right speaker: quiet piano
left speaker: loud guitar
Pan
It's much less common to come across a pan control in everyday life - pan controls are more often seen on studio equipment and music arrangement/sequencing software. A pan control is used to place a sound to the left or right in the stereo field, so you might use it to make the recording in the example above from a piano track and a separate guitar track. It would be less useful on your home stereo than balance, as shown using the same example as above:
-----|----- PAN CENTRED
right speaker: piano
left speaker: guitar
---------|- PAN 90% RIGHT
right speaker: piano and some guitar
left speaker: quiet guitar
-|--------- PAN 90% LEFT
right speaker: quiet piano
left speaker: guitar and some piano
The pan control is taking some of one channel, moving it over to the other channel and spoiling the stereo experience you get when listening to your Britney. And we can't have that.
Stupot points out that although stereo pan (as described here) does exist, it's not terribly useful and therefore pretty
rare, whereas balance controls are far more commonly found in stereo. So that's another difference!
Sources and further information
Pure Motion - http://www.puremotion.com
Stupot and his boss, who know about this sort of thing :)