Alternatively referred to as an account name, login ID, nickname, and user ID, username or user name is the name given to a user on a computer or computer network. This name is commonly an abbreviation of the user's full name or his or her alias. For example, an individual known as John Smith may be assigned the username smitj, the first four letters of the last name followed by the first letter of the first name.
Usernames allow multiple users to use the same computer or online service with their personal settings and files. When used on a website, a username enables you to maintain personal settings and identification with that website or service.