signature

In computing, personal information appended to a message by the sender of an e-mail message or Usenet posting in order to add a human touch. Signatures, which are optional, usually carry the sender's real name and e-mail address, and may also include the writer's occupation, telephone number, and the URL of his or her home page. Many have a short quote, motto or slogan, and a few incorporate ASCII art. .Sig is the name of the file in which signature information is stored on a Unix system.