"CC" in an email stands for "carbon copy." It is a way to send a copy of an email to someone who is not the primary recipient of the email. When you CC someone on an email, they will receive a copy of the email along with all other recipients, and their email address will be visible to everyone who received the email.

For example, if you are sending an email to your colleague but also want to keep your supervisor in the loop, you can CC your supervisor on the email. This way, your colleague will be the primary recipient, but your supervisor will also receive a copy of the email.

It's important to note that there is also a "BCC" field in email, which stands for "blind carbon copy." When you BCC someone on an email, they will receive a copy of the email, but their email address will not be visible to other recipients. This can be useful when you want to keep someone in the loop without revealing their email address to other recipients.