Categories are used in the Posts section of your website. Carefully thought out categories allow posts to be grouped and aids visitors in finding what they are looking for.
Each post can use one or more categories.
Creating Categories
From left side navigation, click Posts and choose the “Categories” link
At this page, you are able to add new categories and what their slug will be. If you do not add a slug name, WordPress will use the category name as the slug. This screen shot shows the existing categories and a count of how many times they have been used.
Adding a Category to a post page
When creating your post page, all available categories appear on the right side navigation under the Post tab. Check all categories that apply.