Every alias for a computer or server is associated with a specific CNAME in the DNS database. Consider, for example, a set of URLs (Uniform Resource Locators) that all belong to a single organization and that all direct online visitors to the same Web site. Each of these URLs is an alias for a single canonical name that is associated with an IP address in the DNS database.Content Continues Below
In addition to facilitating the use of multiple URLs for a single Web site, CNAMEs can be convenient when a well-known organization changes its canonical name. The CNAME will then redirect people who enter an old URL to the correct Web site, even if the old URL is no longer official.