Waves

A wave is a way of transferring energy from one point to other.

Longitudinal waves

This type of wave works by particles pushing against each other. A best example of this is sound: the generator (vocal chords, speaker), pushes the air forth and back; The particles push each other and the energy is transferred along the way.

Transverse waves

More complex, transverse waves can work both physically (S waves) and radiate (electromagnetic spectrum). More likely, transverse waves will be referred to radiation. The transverse waves work by going up and down, without need of any particles (it can go through vacuum).