Collections are one of the most important aspects of the management lifecycle. While "collection" doesn't really denote anything semantic, they can help make content more findable. For example, you might use a collection to group commonly used placeholder images, or a staff gallery that updates every few months. Items that you use often that might otherwise be difficult to find quickly.
From the main content view and search view, you can easily add items to new or existing collections.
Collections are so fundamental to CEO, they can be added and appended by any user.