fiber optics in networking

When is fiber optic cable used. I’ll be honest I probably have a tough time even recognizing it when I see it. I believe I’ve only seeing the cat cable stuff. I don’t see it being used to connect to the computers they usually have ethernet ports that connect to the wall jacks. The switches I’ve seen seem to have cat cables that connect to the patch panel which seems to have cat cables punched down. I haven’t had a chance to look closely at the commercial routers to see what cables run to them. I hear a lot of talk about fiber. Where does this come into place is there something inside the comm room that has this fiber connection, but I don’t know what I’m looking at? Maybe something outside the building buried under the ground?