Well this is not quite true, microwaves are usually defined as waves that are larger that millimeters. Microwave communication is like your cellphone or your radio in your car, you can communication without any medium (no cable).
All Electromagnetic waves (microwaves, visual light, gama rays, and anything that can be considered to be carried by a photon). So while light is rarely used in over the air communication it can be.
Microwaves are a way to communicate with out a medium.
The wave supports itself like this: the electric field is carried by the magnetic field and the magnetic field is carried by the electric field. Weird concept but it works.