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.