Bundling and Minification is a new feature of ASP.NET 4.
Learn more from this tutorial http://www.asp.net/mvc/tutorials/mvc-4/bundling-and-minification.
It has been promoted as part of ASP.NET MVC 4, but actually does not depend on MVC stack and may by used within any ASP.NET application including ASP.NET Web Forms.
When you start a new ASP.NET MVC 4 application using Visual Studio template, it sets up all what you need to start using this feature, but if you have an existing ASP.NET application (even not MVC), you have to complete following steps to make it works with your app.