How it works...

In SwiftUI everything is made from Views, from the main container that is presented to the app's window, to text, a button, or even a toggle.

Thinking back to how UIKit works, this theory isn't too dissimilar—most objects are a subclass of UIView().

The only fundamental difference is that with SwiftUI, the layout and construction of all this is much more visible; this is the declarative syntax coming into play. The best way to think about declarative syntax is in a functional and logical way.

I want to vertically align items on my view:

VStack {}

I then want to add a Text box:

Text("Swift Cookbook")
 

Then, let's add a button:

Button(action: {
    print("Set Action Here...")
}, label: {
    Text("I'm going to perform an action")
})

Even the construction of the button is declarative itself: set an action; set a label. Everything is just... functional.

Another way to think of this would be similar to...