A circularly polarized light wave is shown in this animation. The electric field vector is represented by the glowing yellow arrow that rotates like the hand on a clock. It is this rotation that gives the term circular to this type of polarization. The two (horizontal and vertical) components of the helical wave are traced out and show how one component lags the other by a quarter wavelength. This differential slowing can occur in materials whose refractive indices vary with orientation of the light polarization and they convert a linearly polarized wave into a circularly polarized wave.
Circular polarization and 3D: Modern cinematic 3D often relies on circular polarization to separate the stereo views. Special circularly polarized glasses are worn to allow only the correct view to enter each eye.