What is SwiftUI?

SwiftUI is an Apple framework for building user interfaces across various Apple platforms including iOS, macOS, watchOS, and tvOS. It provides developers with a unified approach to creating visually rich and interactive applications that can be consumed by all Apple devices.

At the core of SwiftUI lies a hierarchical structure similar to a tree, consisting of nodes and leaves. This structure allows for the creation of complex UI layouts and behaviors in a declarative manner, where changes made to the underlying data automatically propagate through the UI.