Mobile Services allow you to easily build a cloud backend for a Windows Store app. You can use Mobile Services for many common backend tasks including authenticating users, storing and accessing data, and providing push notifications.
Learn the basics of how to work with mobile features in an ASP.NET MVC 4 web application, and then deploy your application to a Windows Azure web site.
ASP.NET Web API is a framework for building web APIs on top of the .NET Framework. In this tutorial, you use the Web API to create a REST service that provides data stored in a SQL Database instance.