ASP.NET Web API is a framework for building HTTP services that can be accessed from various clients, such as browsers and mobile devices, iPhone and tablets. It is very similar to ASP.NET MVC since it contains the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection. But it is not a part of the MVC Framework. It is a part of the core ASP.NET platform and can be used with MVC and other types of Web applications like Asp.Net Web Forms. It can also be used as an stand-alone Web services application. ASP.NET Web API was introduced as part of ASP.NET MVC 4; however, it has its origins in WCF as WCF Web API. This new HTTP service model is simple to develop. Today, a web-based application is not enough to reach it's customers. People are very smart, they are using iphone, mobile, tablets etc. devices in its daily life. These devices also have a lot of apps for making the life easy. Actually, we are moving from the web towards apps world. So, if you like to expose your service data to the browsers and as well as all these modern devices apps in fast and simple way, you should have an API which is compatible with browsers and all these devices.