When I start a new ASP.NET project in Visual Studio, I can create an ASP.NET Web Application or I can create an ASP.NET Web Site.
What is the difference between ASP.
Applications are usually compiled before deployment where as the website makes use of the app_code directory. When anything changes in the app code folder the server will re-compile the code. This means that you can add/ change code with a website on the fly.
The advantage of an app is that there is no re-compiling and so initial start up times will be faster.