1. Alternatively referred to as log, log off, logout, disconnecting, and sign out, sign off is the process of disconnecting from a network or what occurs when your connection is lost. For example, to read your e-mail you login to your e-mail account. When you are done reading your e-mail, you should logout.
Why should I sign off of an account?
Computers and online services do not know who is sitting at your computer, and if the service does not log you off automatically you will remain online. If someone else was to get on your computer this means they could access your account, read your e-mail, or perform other actions to your account.
Is it logout, log out, or log-out?
When spelled as one word, "logout" and "log-out" are a noun or adjective that describes the components required to sign out of an account. As two words, "log out" is a verb that describes the action of signing off an account. For example, the sentence: "You need to log out with your logout information so no one else can read your e-mail." uses both forms of the word.
2. The term sign off is also used to describe the process of disconnecting from a network service such as IRC.
3. When in a Windows FTP session the disconnect command will disconnect from the current session. See the how to use FTP help page for information about disconnect and other FTP commands.
4. Finally, sign off is also a message commonly displayed when a user disconnects from a chat service. Most sign offs are witty quotes, sayings, or advertisements created by the user.