What is polarized light?
The polarization of an electromagnetic wave (made up of electric and magnetic fields) is defined as the direction along which the electric field vector (E) points.
In polarized light, the electric field is oriented in a single direction.
Unpolarized light is "polarized" in all directions. The electric fields are oriented in all directions. The light that we see (with our eyes alone) is unpolarized.
Unpolarized light can be passed through a polarizer (such as polarized sunglasses) to polarize it.