Mirror Site
Due to the popularity of some FTP and Web sites, mirror sites came into existence. They are areas on a computer that "mirror" or contain an exact replica of the directory structure of another computer. If you have trouble getting connected to an FTP site, for example, because of the high amount of traffic, you can usually connect to a mirror site that contains the same information on a different computer. Mirror sites are usually updated once a day.
found this on google's Mirror Site