Use categories to keep related datasets in one place where they can be easily located.
Page builders can use categories on the App contents screen to organize pages — this is particularly useful if you have lots of pages in an app. For example, you might have a Sales category, and a Finance category.
Any pages without a category are listed under Uncategorized.
The menu on the left of the screen provides easy access to categories, and any pages that have recently been opened.

You can click the chevron (>) to the left of the category name to display the pages within.