kcarlile did a fine job so I'll just cover what I think was missed. SPDIF is the standard by which digital information is transmitted in audio applications. There are two predominant (and a third that I've never actually run into with my gear) forms that SPDIF take. Coaxial SPDIF uses a normal coaxial cable, like the video line of a red-white-yellow RCA cable to transmit the ones and zeros. TOSLINK uses light through a plastic fiber optic to transmit said ones and zeros. The third form is also fiber based but I forget the name of it. Coaxial SPDIF is an audio only standard.
DVI is a means by which video information is transmitted digitally. The video is then converted into an analog signal for the TV in the case of most projectors or kept in the digital form for DLP, LCD, Plasma, etc.
What makes a cable digital or analog has little to do with the cable. For instance coaxial cables are used both for digital and analog. So long as it's a 75Ohm cable, the two are identical (your right and left channel RCA cables aren't necessarily 75 Ohm as it doesn't matter but it does matter for video RCA and SPDIF). The distinguishing factor is merely how the cable is used. If it's carrying ones and zeros, it's digital. If it's carrying analog, it's an analog cable. Function defines the product.
In reply to:
My coaxial cable caries the audio and video signal into my house from my cable company or satalite dish, in either digital or analog, depending on my subsciption, right?
Pretty much.
