Categories are a way of sorting Services.
In the simplest form, categories are used in the “Browse Categories” functionality available from the Services home to help users find the service they want to request. But categories also help with searching for a service in the search tool, because any service within a category comes up when that category term is searched. Also, it is a category, “Home Page Services” that makes services come up as popular services on the Services home.
By default, the categories provided align closely with the teams provided. This isn’t required. The categories, just like the teams, can be whatever you wish. You can add and rename categories as you wish.