I Feel I Should Know This ......., really basic advice needed please Options

[Jaysee]

I'm a bit embaressed to ask this as I'm sure it must have cropped up on the forum lots of times.
I'm a bit puzzled by the 'optical' audio in and out on the back of my new G5. If they allow one to record audio with such high fidelity why did my apple reseller feel the need to install the MAudio delta44 card/breakoutbox. I'm guessing it has something to do with the 44's higher sampling rate or that the optical ports are somehow 'hard wired' to the OSX 'sound manager' thingy(?)
cheers, jaysee.