The term "Bcc" stands for blind carbon copy. When used in an email, it means that the sender is transmitting a copy of the email to an individual who is not identified in the message. The original email recipient cannot determine that an email includes a Bcc.
Adding Bcc recipients is a way to protect the individuals' identities and email addresses. It also prevents exposure to spam and computer viruses. The Bcc designation dates back to when carbon paper was used to copy typed letters. The opposite of the Bcc notation is the Cc, or carbon copy, designation, which includes a visible list of everyone who receives the email.