Light is a type of electromagnetic wave. It consists of oscillating electrical fields, denoted by E, and magnetic fields, denoted by B. Its properties can be described by studying its electrical field E, although we could just as well describe light and its effects in terms of the magnetic field.
Light waves can vibrate in many directions. Those that are vibrating in one direction – in a single plane such as up and down – are called polarized light. Those that are vibrating in more than one direction – in more than one plane such as both up/down and left/right – are called unpolarized light.