In contrast, online backup is a method of offsite data storage in which files, folders, or the entire contents of a hard drive are regularly backed up on a remote server or computer with a network connection. A number of companies provide online backup services for subscribers whose computers are connected to the Internet, automatically copying selected files to backup storage at the service provider's location. This is sometimes called Web-based backup.
You can read more about online backup on Whatis.com.
Also, our sister site, SearchExchange.com, offers a tip about online versus offline backups for Exchange Server.
This was first published in April 2007