A username is almost always paired with a password. This username/password combination is referred to as a login, and is often required for users to log in to websites. For example, to access your e-mail via the Web, you are required to enter your username and password. Once you have logged in, your username may appear on the screen, but your password is kept secret. By keeping their password private, people can create secure accounts for various websites. Most usernames can contain letters and numbers, but no spaces. When you choose a username for an e-mail account, the part before the "@" is your username.