Categories are one of the two built-in taxonomies used by WordPress and a powerful and versatile way to organize the content on your website.
When you create posts, you have the ability to assign a post to one or more categories. For example, if you’re writing about movies, then you might use categories such as “Sci-Fi” or “Horror.” These categories make it easy for visitors to find all of the content that is related, i.e. all the posts that you’ve written about “Horror” movies.
If you do not select a category for each post, WordPress will automatically assign it the default category. When you first install WordPress, the default category is “Uncategorized.” You can create and/or choose a new default category by clicking on “Settings” from the administration screen and then “Writing.”
Note: You can both select categories and add tags for each post, but categories are different in that they are organized in hierarchies. For example, the “Sci-Fi” category might have two sub-categories underneath it, “Live action” and “Animated.”
There are two ways to create new categories. The first is when you are creating a post. On the right-hand part of the screen, you’ll see a section called “Categories.” You can click on “Add new categories” and create a new category, being sure to slot it into the appropriate hierarchy.
The other way to manage categories is from the administration screen. Click on “Posts” in the left-hand column and then “Categories.” This lets you create new categories as well as organize existing categories. Although it is not mandatory, you can also create a custom slug for each category or a URL-friendly (i.e. no spaces) version of the category’s name.
Note: Deleting a category does NOT delete any posts that were assigned the category! The affected posts, if they have no other category, will be assigned the default category.