What does Bcc stand for in an eamil?

BCC stands for Blind Carbon Copy. The email does go to the recipients in the BCC list but their names are invisible to the the other recipients of the mail.

Even if a mail recipient does a reply-all, the reply is not sent to the mail addresses in the bcc list.

So, one cannot make out to who are in the bcc list. For example, if you want to send a mail to your peer, you want your boss to see that mail but you do not want your peer to know that you have sent it to your boss, then put your peer in the To list and your boss in the BCC list.