Uniform Resource Locator.
When using the address Siteseen.co.uk. (which is a domain name) this informs us of where to find the site, however, it does not tell us how the browser should access the Internet site (HTTP), and what server it should access (the World Wide Web).
We therefore use the URL i.e. http://www.siteseen.co.uk. This now tells our browser how, what and where!