Xamarin is a cross-platform mobile app development platform that allows developers to create native apps for iOS, Android, and Windows using C# and .NET. It enables developers to share code across platforms, reducing development time and cost.
PhoneGap is a free and open source framework for creating cross-platform mobile applications with HTML, CSS, and JavaScript. It allows developers to build apps for multiple platforms, including iOS, Android, Windows, and more, all from a single codebase.