You will hear this when you send an email or you will see people talking about this.
CC means Carbon Copy
BCC means Blind Carbon Copy
If you want to send an email to your staff and also if you want to notify your supervisor about the same email, in the TO field of the message, type the supervisorï¿½s email address and in CC field enter the other staff email addresses.
So basically To means to whom the email is intended for CC means you want the other person also to be notified that you have send a mail TO some one.
Now use BCC when you do not want the TO and CC persons to know that you are copying this email to someone else at BCC.
So going back to the same example, Send the email TO your staff and CC your supervisor and BCC your boss. Now your staff and supervisor will not know that you have send the same email to your Boss. Which is why this is called Blind Carbon Copy (BCC)