Yes, you can CC someone on a ticket. When composing a reply, you'll find various options available, including the CC option.

By selecting CC, a line will be added to the top of the reply box, allowing you to easily add the recipients you want to include in the CC list.

 

 

If you CC an Agent in on your email reply, the Agent will be added to the Ticket as a follower (provided you have the correct permission to do that).

If you CC a User in on your email reply, the User will be added to the Ticket CC Field.

If a User CCs another User, they will be added to the CC field (depending on helpdesk settings).

If a User CCs an Agent, by default, they will not be added as a follower to the Ticket, although your Admins can enable that.