In iOS, a view object means anything that is capable of drawing itself in a rectangular region on an iOS screen.
Let's back in the code for the FirstApp project. In ViewController.swift file we are using a view
to change the background color.
Now we might describe this as empty, but it is not, because it is a view object configured to draw itself and to fill all available screen size on whatever device it runs on.
So in our FirstApp project, all these labels, and a button are all independent view objects. They are currently all nested inside this larger generic view object, and you can see them in Document Outline.So as this is our top-level view object, all these labels and this button are inside it, so they are all subviews of the top-level view. This idea of views with subviews inside them is useful because in the code we could ask this top-level view to give all of its subviews.