When creating views, you are implementing certain business logic and saving it for future use. In some cases, that business logic might be too complicated, or it might just be logical to split the view definition into several different related views.
In Panoply, you can create a view that depends on a different view instead of an actual table. This will create a dependency chain between the views, and therefore you will have the ability to reuse smaller transformations that can be used in multiple different places and/or views. You can identify the dependencies of each view to keep track of which view is affecting what.