Difference between Codebehind and code file

Question

Hi,

 Whenever I create project File-->New --> Project ---> Web Application create in cs file show codebehind file
but oterwise  I create project File-->New --> Website-->  mean
i will get Codefile.

Parser Error

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: Could not load type 'NWO.Web.Global'.

Source Error:

Line 1: <%@ Application Codebehind="Global.asax.cs" Inherits="NWO.Web.Global" Language="C#" %>