Uniform Resource Locator (URL):

Complete address of a web site is called URL or “web address”, It is always unique for a web page.e.g www.questionat.com
A URL is made up of several parts. The first part is the protocol, which tells the web browser what sort of server it will be talking to in order to fetch the URL. In above example the protocol is http.
The second part of the example URL above is the fully qualified domain name of the web site to connect to. In this case, the fully qualified domain name is www.questionat.com. This name identifies the site containing the page. The term fully qualified domain refers to a complete web site or other computers name on the internet. The term domain name usually refers only to the last part of the name, in this case yahoo.com, which has been registered for that particular company’s exclusive use.

URL Example:

The third part of the example URL, is the path at which this particular web page is located on the web server. In this case, path is /weather/Lahore/weather.html similar to a filename, path usually indicate where the web page is located within the web space of the web site; in this case it is located in the Lahore sub-folder of the weather folder.