The Categories API allows components to register new categories with the categories framework. These categories can be selected inside Web Access rules and used to classify content.
The Categories API only provides useful functionality when used in conjunction with APIs that provide classification of content like the WebActivity API.
When categories are registered you can optionally register a provider of the category at the same time. A category that has a provider appears in the UI with the provider name next to it so a user can see where the category came from. Additionally, a provided category cannot be deleted by a user and can only be deleted by the original provider.
Components can also register their use of categories (Whether or not they originally provided it) which also appears in the UI, allowing the user to see where a category is being used. Categories that have registered users cannot be deleted manually by the user. This is useful for a component that allows a user to select a category as part of its configuration. The component would then register its use of the category and the user could see that the category was being used by that component.