Flutter is an open-source UI software development kit created by Google. It is used to develop cross platform applications for Android, iOS, Linux, Mac, Windows, Google Fuchsia, Web platform, and the web from a single codebase. Native app development involves coding an application specifically for one platform, such as iOS. On the other hand, cross-platform app development entails building an application that works on multiple platforms using a single codebase.

Flutter, a standout cross-platform development framework, offers several advantages:

1. Close-to-Native Performance
2. Fast, Consistent, and Customizable Rendering
3. Developer-Friendly Tools
Flutter’s approach to cross-platform development combines close-to-native performance, consistent rendering, and user-friendly tools, making it a compelling framework for developers.