Sorry if this is obvious to you lot but as a person who does not use email a lot I want to know what the "add Cc & add Bcc" bits do when you compose an email.
These allow you to add other email addresses to the email. E.g. you might want to tell someone that you have paid their invoice, and also let your accountant know. In that case, you'd add your accountant's email address into the .cc field.
When you add an email address into the .bcc field, that person will see the email, but the main recipient won't be aware of it, hence "blind" carbon copy.
Add Cc is Add Courtesy copy - to someone for information only, they would not normally be expected to do anything or even reply. Name is seen by the 'To' list.
Add Bcc is Add Blind Courtesy copy. As above but also the main 'To' recipient(s) do not see that the person has received the email.