I have some basic doubts regarding how the energy is transfered (e.g. transmission of radio waves) as EM waves. As I know, the wave is not anything that can be practically seen in the space, but it is a model that we use to describe how energy is transferred. But if we think practically, how does actually the energy transfer through vacuum or a medium? In vacuum, as there's nothing inside, how does the energy transfer? I've read about 'radiation', but what is actually used for the energy transfer?