I can't understand how light gets "polarised" and how it filters through different polariser in terms of its electric and magnetic field ?

In terms of electric and magnetic field how does a polarimeter works.

Why do optically active molecules show this rotation/how they bring about the rotation of light.

What laws it follows.

What do the half dimmed semi-circles in the polarimeter eyepiece signify ?

I can't picture light changing directions, pls explain me !!!