A CC, or carbon copy, is an exact copy of an e-mail. When a receiver gets a message, she can see who else the message was sent to, and she can also see who got a CC, of the email. Those that get a CC get the exact same message as those that are listed as receivers of the message. If you wish to make a CC hidden, you can do this by turning the CC into a BCC, or blind carbon copy.
Compose an e-mail message as you normally would, and put the recipient's address in the "To" field.
Choose the addresses of the people that you want to get a CC of the message and that do not need to be hidden. Type those e-mail addresses into the "CC" field.
Choose any addresses that you want to send a CC of the email to but you wish to remain hidden. Type those addresses in the field marked "BCC." This means that they will be sent blind carbon copies. They will see the entire e-mail and who it is to, but neither those listed in the "To" field nor those listed in the "CC" field will see that they have got the message.
You can place all of the addresses in the BCC field to hide them from each other. However, you must have at least one address in the "To" field to send the message. If you wish to hide all the addresses from each other, you can place your own address in the "To" field and everyone else's in the BCC field.