[Page: 1] Here you can see all categories and its sub categories in sorted order.
This is a category. Only posts can be assigned to a category, but it is not necessary, so categories are optional. If you want to use them, you have a lot of space here to describe the content of your category, include images and other stuff like in a posts content. It is even possible to nest categories unlimited, but for the sake of user experience, I recommend not overdoing it. 😂