What are major events in GLOBAL.ASAX file

The Global.asax file, which is derived from the HttpApplication class, maintains a pool of HttpApplication objects, and assigns them to applications as needed. The Global.asax file contains the following events:

Application_Init: Fired when an application initializes or is first called. It's invoked for all HttpApplication object instances.

Application_Disposed: Fired just before an application is destroyed. This is the ideal location for cleaning up previously used resources.

Application_Error: Fired when an unhandled exception is encountered within the
application.

Application_Start: Fired when the first instance of the HttpApplication class is created. It allows you to create objects that are accessible by all HttpApplication instances.

Application_End: Fired when the last instance of an HttpApplication class is destroyed. It's fired only once during an application's lifetime.

Application_BeginRequest: Fired when an application request is received. It's the first event fired for a request, which is often a page request (URL) that a user enters.

Application_EndRequest: The last event fired for an application request.

Application_PreRequestHandlerExecute: Fired before the ASP.NET page framework
begins executing an event handler like a page or Web service.

Application_PostRequestHandlerExecute: Fired when the ASP.NET page framework is
finished executing an event handler.

Applcation_PreSendRequestHeaders: Fired before the ASP.NET page framework sends
HTTP headers to a requesting client (browser).

Application_PreSendContent: Fired before the ASP.NET page framework sends content
to a requesting client (browser).

Application_AcquireRequestState: Fired when the ASP.NET page framework gets the
current state (Session state) related to the current request.

Application_ReleaseRequestState: Fired when the ASP.NET page framework completes
execution of all event handlers. This results in all state modules to save their current state data.

Application_ResolveRequestCache: Fired when the ASP.NET page framework completes
an authorization request. It allows caching modules to serve the request from the cache, thus bypassing handler execution.

Application_UpdateRequestCache: Fired when the ASP.NET page framework completes
handler execution to allow caching modules to store responses to be used to handle
subsequent requests.

Application_AuthenticateRequest: Fired when the security module has established the
current user's identity as valid. At this point, the user's credentials have been validated.

Application_AuthorizeRequest: Fired when the security module has verified that a user
can access resources.

Session_Start: Fired when a new user visits the application Web site.

Session_End: Fired when a user's session times out, ends, or they leave the application Web site.