"CC" and "BCC" are different modes of addressing a message to someone, rather than simply adding them to the "To" list.
Anyone listed in the CC field of a message receives a copy of that message when you send it. All other recipients of that message can see that the person you designated as a "CC" recipient has received a copy of the message.
BCC is similar to the "CC "feature, except that all recipients listed in the BCC field are invisible to all the other recipients of the message (including other "BCC" recipients).
Please note, every message must have at least one person on the "To" list.