Reprinted to http://blog.csdn.net/wulex/article/details/51861972

iisreset -- The object is the entire IIS server, which stops the World Wide Web Publishing Service and restarts the service, so all websites stop the service first and then restart the service.

As pointed out, 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.

Recycling -- Object is an Application Pool, under which IIS will create a new process and maintain the original process for the time being. After a new process is established, all new requests are transferred to the new process, and then the original process is closed for a period of time. (There's still some doubts here. Will the old request go directly to the new process or continue to be served by the original process? To be verified)

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 automaticaly. You usualy 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).

Restart -- The object is a Web site, and all services remain in the same process pool. But all sessions are disconnected and reconnected.

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.

Refresh -- The object is IIS Manager itself, which does not affect any services, but refreshes the tree list on the left.

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