I keep doing classes and typing away at learning programming and in a few different lesson they say this is how you declare a null variable(java and Kotlin if i remember right python is a "none" not exactly the same). 

But everything I read or learn says don't do it. 
Why do it or is there a legitimate use for one?

REV 1.0 Below

I edited and rolled this question back some because a none after some more digging into the subject acts very similar as a null.

Instead of changing my question please make comments on how i can look at it differently or reframe or ask better questions.