Categories can be used to separate publications and to keep them organised. You can create a separate domain for a category to make sure people can reach a category directly.
In the dashboard go to settings and under the general tab you will find the category button.
When you add a category there are a few simple options to configure as you can see below. The position input field can be used to change the order of the categories. You can fill in any number and the categories will be shown in the right order.