XNA is a game development framework that was originally developed for Xbox 360 but also supports Windows, Windows Phone, and other platforms. It provides libraries and tools to help developers easily create 2D games. MonoGame is an open source implementation of XNA that allows developers to port XNA games to additional platforms like macOS, iOS, Android, and Linux. Both tools utilize a basic game loop structure of initializing resources, updating game logic, and drawing to the screen each frame.