What is UIHostingController?

UIHostingController- A UIKit view controller manages a SwiftUI view hierarchy. It is intended when integrating SwiftUI views into a UIKit view hierarchy.

 Present a SwiftUI view in the  UIKit view controller

let swiftCustomUIView = SwiftCustomUIView()
let hostingController = UIHostingController(rootView: swiftCustomUIView)
present(hostingController, animated: true, completion: nil)

What is SwiftUI?

SwiftUI is a user interface (UI) framework developed by Apple that differs from iOS frameworks in several ways,

• Declarative

• Compatibility 

• Responsiveness (Reactive)

• Preview Feature

• Code Reusability

• Reduced Code

UIKit is better for maintaining legacy apps and SwiftUI is a good choice for new projects.