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.
For example, the URL http://example.org/wiki/Main_Page refers to a resource identified as /wiki/Main_Page whose representation, in the form of HTML and related code, is obtainable via Hypertext Transfer Protocol (http) from a network host whose domain name is example.org.
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.