what is the difference in audio or video cables?

Audio and video cables can be changed intercheangeably. There are many manufacturers who's video cables are the same as their analog and or digital cables.

From what I have read, audio cables are more sensitive to differences in such things as shielding and dielectic. So whereas you would find people who believe that unshielded audio cables produce a better sound, I have never heard/read of any videophiles who thought an unshielded video cable produced a better picture. As long as the cable is properly shielded, it'll generally work well as a video cable. The dielectic used also affects audio more than video. For instance, you'll probably hear more difference with a teflon cable than a foamed PE than see a difference between the two. The only thing I would be careful with is using digital cables in other applications. Some digital cables simply don't seem to work as a video or analog cable.

You did not mention brand, but the most basic of these are very similar. Construction is typically coax, with copper or copper plated center conductor, surrounded by foam dielectric and a shield of copper braid or aluminum foil.

The best cheap cables of these types is made by Belden and available as component video and / or audio cable.

For component video, Belden 7710A coax (a three-conductor version of 1694A), or audio, Belden 1505F. Both support RCA connectors.

There are differences when you leave this basic design and go with audiophile cables such as Cardas, Purist, Nordost and the rest. Whether the performance gain warrants the investment is up to you.

There is no difference. It's just marketing, the cables are simply cables. Use them for whatever you like, except digital connections for which a true 75ohm connection is best.