Categories and tags are WordPress features that allow you to classify and organize your posts in different ways.
The only difference between categories and tags is that categories can be organized hierarchically. Categories and sub-categories can therefore be created.
Categories allow you to organize articles according to a hierarchy of content.
Tags, although less important, have rather the function of keywords and make it possible to organize and thus to be able to find contents in a more transversal way or with the help of search engines.
Example for the category Cuisine, we could have the sub-categories Chinese, Lebanese, terroir, etc.. We could also add the labels vegetarian, gluten-free, etc. So a user could search for Lebanese and vegetarian recipes.