What is an URL
An Uniform Resource Locator (URL) is the term used to identify an Internet resource, and
can be specified in a single line of text.
What is an URN
An Uniform Resource Name (URN) is the term used to identify an Internet resource, without
the use of a scheme, and can be specified in a single line of text.
What is an URI
An Uniform Resource Identifier (URI) is used by a browser to identify a single document,
and it too can be specified in a single line of text.
URL vs. URN vs. URI
The difference between the three is subtle. An URL refers to a Web page, including the
scheme, but without a name location. An URN may also include the location of a code
fragment. An URI refers to a Web page including the location of the code fragment, if one
exists, and the scheme.
URL http://www.gleaners.org/faq.html
URN www.gleaners.org/faq.html#Q04
URI http://www.gleaners.org/faq.html#Q04
Because Web servers allow for default documents and do not require a scheme to retrieve a
document, the subtle difference between an URL and an URN and an URI is hard to tell. URL
is now used as the generic term.
Additional information on URL specification may be found at http://www.w3.org/Addressing/