Categories and tags can be used to organize blog posts similar to how a book is organized with a table of contents and an index.
Categories could be considered your blog’s table of contents. Each parent category is a chapter, and each child category is a section within that chapter. A common mistake that many blogs make is to have dozens of categories in a flat hierarchy with no child categories.
To better organize posts, try to stick with less than ten parent categories, and group the rest of the categories below these as child categories.
Tags have a flat hierarchy and are similar to a book’s index. Tags can be used as keywords to further specify the content of a blog post or link together disparate posts.