A uniform resource locator (URL) is a way of unambiguously describing the location of something on a network. This something can be a web server, printer, ftp server, or even another desktop computer. Most commonly, a URL refers to a website or web page.
The URL was a fundamental innovation in the history of the Internet. It was first created by Tim Berners-Lee in 1992 to allow document authors to establish hyperlinks on the World Wide Web. Since 1994 the URL concept has been subsumed into that of the more general Uniform Resource Identifier (URI), but URL is still a widely used term.
As an example, the URL for this website is http://infolific.com/ while the URL for this page is http://infolific.com/technology/definitions/internet-dictionary/url/. To find the URL of any web page you're looking at, simply look at the top of the web browser you're using.