An Internet address typically starts with a protocol name, followed by the name of the organization that maintains the site; the suffix identifies the kind of organization it is. (A protocol is a set of rules and standards that enable computers to exchange information.)
For example, the address http://www.yale.edu/ provides the following information:
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.