As described elsewhere, GetCategories returns core information about each category such as the category name, ID, level in the hierarchy, and so forth. It also returns information about each category's parent ID so that you can build the category tree within your application. Additionally, GetCategories returns information about a few listing features that are supported by individual categories.
Because the amount of data returned by GetCategories can be quite large, users can call GetCategoryFeatures instead to retrieve information about certain features that are available for one or more categories.
To determine which item specifics are required/recommended/available for a category, call the getItemAspectsForCategory method of the Taxonomy API.
When issuing calls such as GetCategoryFeatures, you may need to combine the results with information from GetCategories in order to build a complete set of information about an individual category and the features it supports. For example, GetCategoryFeatures returns category IDs but it does not distinguish between parent and leaf categories, while GetCategories does indicate which categories are leaf categories.