The Persian Empire was conquered by the Greeks led by Alexander the Great. Starting in the year 334 BC, Alexander the Great conquered the Persian Empire from Egypt all the way to the borders of India.
In information technology, a Uniform Resource Identifier (URI) is a string of characters used to identify a resource. Such identification enables interaction with representations of the resource over a network, typically the World Wide Web, using specific protocols.
A URL is a URI but a URI is not a URL. A URL is a specialization of URI that defines the network location of a specific representation for a given resource. Taking the same W3C example, there are actually 2 representations available for the w3c_home resource: http://www.w3.org/Icons/w3c_home.gif.