Answer
MAUI runs on Windows via WinUI 3 (Windows App SDK) and on macOS via Mac Catalyst (running the iOS UIKit stack on the Mac). One codebase produces desktop apps alongside mobile, though desktop adds concerns like resizable windows, menus, and pointer/keyboard input.
Real-world example A productivity app ships to the Microsoft Store (WinUI) and the Mac App Store (Catalyst) from the same MAUI project.