What does cc mean on an email?

It stands for "carbon copy", which refers to the idea that someone else is receiving (being copied on) the email/mail. Carbon copies were literally used back when physically mailing something to someone. The copy (cc) that someone would receive was literally a carbon copy of the original document or writing. Nowadays in emails the term "cc" is still used, but simply to notify others of who is being copied or also receiving the message.

Bcc stands for Blind carbon copy and if you send an email to person 1 and then send a blind copy to person 2 then person 1 wont know that you sent the copy to person 2.