In telecommunications, the material substance along which a signal propagates
is called "transmission medium" or "media". A medium can be
guided, that means it needs some kind of cable, or unguided, if the information can be transmitted wirelessly .
As you can see in the graphic on the right hand side there are many different
kinds of media such as twisted-wire pair, coaxial
cable, waveguide, optical
fiber or radio path.
Chose a medium from the drop-down menu and see how it looks like!