URL stands for Uniform Resource Locator and denotes the address of the resource on the Internet. An Internet site address typically starts with a protocol name followed by the organization that maintains the site; the suffix identifies the kind of organization. For example, http://www.isye.gatech.edu/ identifies the Web server at the School of Industrial and Systems Engineering at the Georgia Institute of Technology. "http://www" indicates that it is a Web server that uses the http protocol, and ".edu" identifies Georgia Institute of Technology as an educational institution. Generally, commercial site addresses end with ".com" and government site addresses end with ".gov".
If the address points to a specific page, additional information such as a port name, the directory in which the page is located, and the name of the page file, is included. Web pages authored by using HTML (Hypertext Markup Language) often end with an .htm or .html extension. For instance my home page has an address or URL of http://www.isye.gatech.edu/~mgoetsch/index.html.