To really understand classical EM waves you need to know a little bit about electricity and magnetism, specifically
Maxwell's equations.
To really understand them takes the better part a semester course (and that's just to a basic level), but I'll try the three minute version:
Charged particles create an electric field that causes a force on other charged particles. Changing electric fields create a magnetic field. Magnetic fields produce a force on
moving charged particles. Changing magnetic fields produce electric fields.
Since changing electric fields produce magnetic fields and changing magnetic fields produce electric fields, it's possible to produce a self-sustaining wave of changing electric and magnetic fields without any electric charges nearby. The electric fields changes in such a way that it produces a changing magnetic field that in turn produces a changing electric field and on and on at the speed of light.
These fields are produced at right angles to each other and the direction of propagation. The polarization direction of the electric field. A polarizer has a conductor parallel to one of the directions and not the other. Light polarized along that direction will be absorbed and light polarized along the other direction will be transmitted.