The document compares ASP.NET Web API and ASP.NET MVC. ASP.NET Web API is focused on outputting raw data through HTTP services, while ASP.NET MVC is focused on outputting HTML views. Some key differences include: ASP.NET Web API assumes data comes from the query string or form body, while MVC assumes multiple sources; Web API supports content negotiation and self-hosting, while MVC does not; and Web API is better for non-browser clients while MVC is optimized for browsers. Both can be used together in a single project.