The Content page is one library for the whole workspace. Everything you have added is here, whatever type it is.
The library
Folders, the details shown against each item, what deleting actually removes, and how to get your own files back out.
In this section
Folders
Group content by campaign, site, or team. Folders organize the library and have no effect on what plays.
What the library tells you
Dimensions, duration, resource type, status, and the URL, read from the file itself so nobody has to type them.
Deleting content
Deleting from the library pulls an item from every playlist at once. Removing it from a playlist does not.
Getting your content back
Every asset carries a source_url you can fetch yourself with the CLI or the API. Keep your originals in your own storage.