XCode is Apple's software development environment for iOS and Mac OS app development. As the new Swift programming language comes with it built-in, it helps us tremendously in shipping quality iPhone, iPad and Mac apps.
Xamarin is Microsoft's entrant into the app development marketplace. It makes it possible to create mobile apps for both iOS and Android by writing one, shared set of code.
A well designed and developed website is worthless without proper optimization. A well optimized website research about the needs of it's visitors, resulting in content that is tailored to their needs.