The content structure gives you an overview of how your views and collections are organised.
You can sort, add and remove collections directly in this overview. You will need to save the changes before they will be visible in your service.
You can also see which collections you have created but haven't added to any page at the moment. They are considered to be inactive.
This feature will help you to organise your content in a better way and to understand how and where your collections are included.