Favorites is a particular collection that enables you to bookmark documents. The list of documents bookmarked as favorites is available:
On the dashboard in the Favorite Item widget
Or on the Favorites Tab in the side menu
Bookmarking documents in your favorites can be done like when you add documents to a collection and selecting the Favorites collection, or using the Favorites icon from the document itself.
Once the document is added to your favorites, it will be available in the dashboard and in the Favorites tab. Your Favorites are saved browser-side, which means that if you use another browser you will lost your favorites.