How to Build WordPress Categories
In WordPress, a category is what you determine to be the main topic of a blog post. Through categories, you can file your blog posts into topics by subject. To improve your readers’ experiences in navigating through your blog, WordPress organizes posts by the categories you assign to them.
Visitors can click the categories they’re interested in to see the blog posts you’ve written on those particular topics. You should know ahead of time that the list of categories you set up can be displayed on your blog in a few places, including the
Body of the post: In most WordPress themes, you see the title followed by a statement, such as “Filed In: Category 1, Category 2.” The reader can click the category name to go to a page that lists all the posts you’ve made in that particular category. You can assign a single post to more than one category.
Sidebar of your blog theme: You can place a full list of category titles in the sidebar by using the Categories widget included in your WordPress installation. A reader can click any category and go to a page on your site that lists the posts you’ve made within that particular category.
Subcategories (or category children) can further refine the main category topic by listing specific topics related to the main (parent) category. In your WordPress Dashboard on the Manage Categories page (choose Posts→Categories), subcategories are listed directly below the main category. Here’s an example:
Books I Enjoy (main category)
Trashy Romance (subcategory)
For Dummies (subcategory)