Iis – Command to display on which application pool the specific website is running

The IIS_Anonymous account is the the account that the user accessing the site runs as. So you want to make sure that this user can't access any files outside of the web root and files with sensitive information IE sql connection strings etc. You generally don't want to allow this user write access anywhere.

The App pool account is the account your app (or the IIS server) runs under. You want to give this account the bare minimum access it needs to run your script. If you are security conscious you will create different app pools for each site, so that a security misconfiguration on one site will not leak to another.

iisreset will stop and start the World Wide Web Publishing Service. This, of course, applies to all of your application pools. I'm sure you noticed a process being created for each application pool. This process will handle requests for all websites associated with it. When you recycle an application pool, IIS will create a new process (keeping the old one) to serve requests. Then it tries to move all requests on the new process. After a timeout the old process will be killed automatically. You usually recycle your application pool to get rid of leaked memory (you might have a problem in your application if this needs to be a regular operation, even though it is recommended to have a scheduled recycle). As for restarting a website, it just stops and restarts serving requests for that particular website. It will continue to serve other websites on the same app pool with no interruptions.

If you have a session oriented application, all of the above will cause loss of session objects.

Refreshing a website has no effect on the service/process/website and is merely a UI command to refresh the treeview (maybe you added a directory you don't see in the management console).