URI - Uniform Resource Identifier
URL - Uniform Resource Locator
A URI _identifies_ a resource by meta-information of any kind.
A URL _locates_ a resource on the net, which means if you have
a URL and the appropriate protocol you can retrieve the resource.
One characteristic of a URI is, that it gives information about
exactly one resource. Another is there can be more than one URI
describing the same resource.
That was the theory, here is an example:
URI: <URL:
http://www.w3.org>
URI: <URL:
http://www.w3.org/>
URL:
http://www.w3.org/pub/WWW/>