How does a linear light polarizer actually works?

What you need is to learn how to research so you can know a few things. Your first stop is google.com where you search a few words and see what you get, like this: www.google.com/search?q=linear+light+polarizer

Your second check is wikipedia.org where you find this: en.wikipedia.org/wiki/Polarizer

And the next place is one or more of the links at the end of the article. Most of the time you will have learned what you want to know by the time you get this far.