URL is short for Uniform Resource Locator and is also sometimes used instead of URN (Uniform Resource Name) or URI (Uniform Resource Identifier) when there is a technical discussion about those as they relate to basically the same thing. URL’s are most often used to access web addresses (http:) but can also be used to transfer files (ftp:) access email (mailto:) or telephone numbers (tel:) in addition to many other applications.
URL’s were standardized in 1994 as an outcome of a collaboration that was begun in 1992. The format that resulted is the familiar combination of domain names with a file path syntax, using slashes to separate directory and file names. URL’s are not case-sensitive so can be written in all lowercase, all uppercase, or any combination. If one knows the IP address of a website then it may be used instead of the domain name in that portion of a URL.