"CC" is the short form of Carbon Copy. When you send a message to more than one address using the CC field, both the original recipient and all the recipients of the carbon copies see the To: and CC: fields including all the addresses in them. This means that every recipient gets to know the email addresses of all the persons that received your message.
"BCC" is the short form of Blind Carbon Copy. The BCC field helps you deal with the problems created by CC. As it is the case with CC, a copy of the message goes to every single email address appearing in the BCC field. The difference is that neither the BCC field itself nor the email addresses in it appear in any of the copies. The only recipient address that will be visible to all recipients is the one in the To: field. So, to keep maximum anonymity you can put your own address in the To: field and use BCC.