In the CC (carbon copy) box you usually enter recipients who are to get a copy of the e-mail for their information.
In the BCC field (blind carbon copy) you also enter recipients who are to receive a copy of the e-mail. The difference between BCC and CC box is that no other recipient is informed who else has received a copy if you send a mail with BCC. If you enter e.g. 10 recipients in the BCC box of a mail and send the mail, it is as if you sent ten e-mails to ten recipients individually.