When composing email you will see fields like TO, CC and BCC above the text area.
TO, (to whom) is the person exactly whom you are sending the email. Generally the whole purpose of the email is to express or pass information to the person who is in the TO field.
CC stands for Carbon Copy. When writing emails the actual recipients address will be included in TO field of the mail application.
People who ever not directly involved or acting on the subject matter will be included in CC field for informational purpose in such case you can put them in CC.
BCC stands for Blind Carbon Copy, which is exactly similar to CC but the email addresses included in the BCC field will not be visible to anyone else other than the particular recipient.
It’s exactly similar to resending the email to that particular person who is listed in the BCC field separately. Instead of resending it’s easy for the writer to put BCC in the same email.
Note: when you reply by pressing REPLY ALL button the BCC person will not get the reply whereas CC recipients will get them. Even the header of the received email will not contain the email addresses mentioned in the BCC field.