Web API is an API over the web which can be accessed using HTTP protocol, it is a concept and not a technology. We can build a Web API using .NET REST APIs that provide programmatic access to read and write data using which we can integrate our capabilities into our own application.

The ASP.NET Web API framework includes a HttpClient to communicate with a Web API server. The HttpClient can be used in an ASP.Net MVC server side app, and it is like a webservice or WCF service but the exception is that it only supports HTTP protocol.