SPDIF cable same as coaxial cable?

S/PDIF refers to the signalling, not the conductor type.

Coaxial and TOSlink are both using S/PDIF
https://en.wikipedia.org/wiki/S/PDIF

Fiber has the advantage of never causing a ground loop, which can have odd effects in digital, which may or may not be audible as a traditional ground loop.

Some swear that copper sounds better, which could have something to do with the connector hardware/drivers. 

I've long ago switched to USB.

op - you should do some basic google searches and read, or if you don't like to do that, try youtube

you ask soooooo many very basic questions

jss49 - The problem with your suggestion is that doing a google search on any subject, audio or otherwise, brings up at least as much bad or confusing information as good. I think it's perfectly reasonable for someone to ask basic questions here where there's a least a somewhat higher probability of getting a useful answer. Fortunately there are quite a few experienced folks here who don't seem to mind helping a newcomer. 

Sfar
kudos for appreciating a need for a good resource for clarity in a very complex area.  Sooooo many suppliers offer very poor Clarity about Their products. People can make very expensive mistakes.  Sooooo nice that this site offers amazing feedback. 

Most people when they say coax mean the digital connection with RCA plugs, optical they say toslink. There is a XLR digital connection as well AES3 which SPDIF is based on.