Updating web services without refreshing

When a webpage has included a webservice in it, that web service gets uopdated automatically without browser refreshing.

If browser does not refresh, then there is no request being sent from browser (client) to server. When there is no request, how does server update the webpage. That is, how does server complete request-response protocol in absence of request ? Is there a mechanism on the server side, which sends out information to all the webservice user, irrespective of rerceiving request from them ? If yes, what is this mechanism called ?

I have read about AJAX, but that also requires initiation on browser side and then that information is sent to the server. While in case of webservices, page has to be refreshed automatically in order for the web page to be kept uptodate. What iss this mechanism ,ho does itwork ?

Thanks.

Hi!
Take a look at this webpage, which I hope you will find useful:
http://www.hscripts.com/tutorials/html/autorefresh.php
Best wishes!