This document summarizes a presentation about developing cross-platform apps using Xamarin. It discusses that Xamarin allows building apps for multiple platforms like iOS and Android using C# while achieving native performance. The agenda covers an introduction to Xamarin, getting started, code sharing between platforms, and reusing native libraries. It also discusses competitors like PhoneGap and challenges like requiring knowledge of each platform and needing a Mac for iOS development. The presentation aims to explain how Xamarin enables building cross-platform mobile apps with native user interfaces and sharing common code.