It is a means of connecting components to your receiver by virtue of a tiny little “optical light”. Some audiophiles argue that the sound can never be as good as being hard wired. I’ve used optical signals for other things, but not my speakers.

There’s a lot to be said for the simplicity of wireless.

You need a home theatre system with an optical input port thingy and then can connect the satellite receiver to it so that you can get 5.1 surround sound with yout satellite TV (where available).

If you’re not connecting through HDMI, optical is the easiest method for connecting sound, one cord, no fuss.

Careful though, unlike normal cords, if you step on an optical it’ll break it.