What is Web API? It is a Framework for building HTTP services on top of the .NET Framework. To get familiarise yourself with ASP.NET Web API then you can read this post here. What is OData? Open Data Protocol is a web protocol for accessing information via services. It is built upon technologies such as XML and JSON. More on this topic can be read here. What is ASP.NET Web API OData? It is a framework that you can use OData services in your Web API application. This post describes the details of using ASP.NET Web API with OData and also outlines the features of ASP.NET Web API OData and steps to create Web API OData service using Visual Studio 2012.