An E-mail address is composed of two parts - a username and a domain name, in the following form: username@domainname.extension. The username is the name you choose to be identified with for e-mail purposes and that you have provided to the e-mail host to create your e-mail account. The extension can be any of many options, such as .com, .org, .fr (country codes), .biz, .info, .gov, .int, etc.