The History of HTML, p.3

HTTP uses a concept called the Uniform Resource Locator or URL (pronounced "you-are-el") to locate any available data object on the Internet or on Internet-worked hosts.

The basic idea behind the URL concept is that, given certain information, you should be able to access any publicly available data on any machine on the Internet.

That certain information consists of the following basic pieces of a URL:
  • The access protocol to be used.
  • The machine on which the data resides.
  • The domain in which the machine resides.
  • The path to the data.
  • The name of the file containing the data.
  • The port from which to request the data.