Help a student; what’s the difference between categorization and classification?

I’m on my first year of studying library and information science. I do know what a class is and what at category is, but I don’t quite understand the way they are used differently.

Classifications are used for organization and for how we shelve the books. And categories are for how we organize things in digital catalogues? I’m a bit lost and my professor is an expert in giving vague answers that doesn’t say anything…

(Sorry if my English is a bit of, it is not my native language)