"re" is an English abbreviation, which means "about" and "about". "cc" is an English abbreviation, which means "carbon copy" and "carbon copy". These two abbreviations are usually used in e-mail to indicate the subject or cc of the message.

If you want to learn online courses, you can try to search for related courses online or sign up for courses on the online education platform. Usually, online courses refer to online education courses conducted on the Internet, which can be studied through computers, mobile phones or other devices.