I noted that so many websites, opening an article, show in the address bar the title of the article, as if it were a subfolder of the main domain...
For exemple, this site: http://www.everyeye.it/serial/notizia/the-walking-dead-4-interviste-da-san-diego-spoiler-_165297 (or facebook if you think thee url of a page of the users).

if I were to create a site that should open articles, the page would be www.mydomain.com/article?id=23

in other words, i pass throught get the id of the article for generate it..
I think that this websites uses the url-rewrite tecnique. Do you confirm?
And how search engines indicizes thoese pages that therorically doesn't really exists??