Part of an e-mail address is typically composed of three parts: the username, the domain name, and the top-level domain. The username is a unique identifier chosen by the user, while the domain name is the name of the organization or company that owns the e-mail address. The top-level domain is the suffix at the end of the address, such as .com, .org, or .net. These three-letter abbreviations are known as DOT (3 letters), COM (3 letters), and ORG (3 letters).