Meaning, you mail one message to one address and it is then automatically re-mailed to everyone subscribed whether ten people or fifty thousand. So that only you, as the list manager are able to post to the list. A mailing list can do that for you quickly and easily. True you can do the same manually using your own email software, but mailing lists were designed to make that effort quick and easy. As you become comfortable with using email and mailing lists the chances are you will develop a small group of people or clients or prospects you wish to contact with the same message.
CC stands for carbon copy.
It will send a copy of your message to the list of addresses you place in that area. However, everyone you mail to gets a copy of your CC list of addresses. That can be counterproductive at times. BCC is Blind carbon copy. That way, the full list of addresses is NOT sent to all 50 people to read through.