What is the Global.asax file?

The Global.asax file, also known as the ASP.NET application file, is an optional file that contains code for responding to application-level events raised by ASP.NET.The Global.asax file is parsed and dynamically compiled by ASP.NET into a .NET Framework class the first time any resource or URL within its application namespace is activated or requested.Whenever the application is requested first time, the Global.asax file is parsed and complied to a class that extends the HttpApplication class.