On the Internet, @ (pronounced "at" or "at sign" or "address sign") is the symbol in an E-mail address that separates the name of the user from the user's Internet address, as in this hypothetical e-mail address example: johnbrown@gmail.com Perhaps because it was one of the standard characters designed for typewriters, the @ was chosen for inclusion as one of the special characters that became standard for computer keyboards, programs, and online message transmission.

Source: TechTarget