QUOTE(shnaggletooth @ May 13 2006, 03:30)

As I read everywhere, "you should only burn wav files that are 16-bit, 44Khz".
That's because that is the only format you can burn on a CD.
QUOTE
Ok, so what exactly are 16-bit, 48Khz files used for? And that goes double for 20-bit and 24-bit sampled wavs.
Higher sampling frequency means higher cut-off frequency. By Nyquist theorem, fc=fs/2. That means that for audio sampled at 44.1kHz the highest recorded frequency can be 22.05kHz, for 48kHz - 24kHz, etc. So higher sample rate enables you to record wider frequency bandwidth. Since human hearing rarely goes beyond 20kHz (if that at all) it doesn't make much sense to use higher sample rates. OTOH, higher cut off frequency keeps more high-frequency transient "quality" (so to speak) so there is some sense in using it
As for bit-depth, it dictates the noise floor. The approximate formula says S/N=6*NumberOfBits (S/N being signal-to-noise ratio). 16bits will give you a little over 96dB dynamic range, 24bits will give you over 144dB.
You also want to use more bit-depth when operating on signal in digital domain. Every manipulation requires some coefficients to be rounded at the end to fit in the word length. This rounding can accumulate and lead to loss of audio quality and detail. So you want your mixer and DAW to operate with higher bit-depth internally, even if it outputs the final mix to 16-bits.
Regards,
Goran Tomas