CMC can include any means by which individuals and groups use the Internet to 'talk' to each other.
CMC can either be synchronous (exchanges take place in 'real time') or asynchronous (messages are posted up at any time, and read and responded to by other users also at times which suit them; in other words, users do not have to be online at the same time, as they do with synchronous exchanges). Email, mailing lists, Usenet and computer conferencing are all asynchronous, while IRC, Internet telephony and videoconferencing all take place synchronously. All of these types of CMC are now available through the Web i.e. through a standard Web browser.
Which type of CMC you use will depend on what kind of discussion you want to take place? Each has their strengths and weaknesses both in terms of technical constraints and the type of interaction that they encourage.
The main technologies include:
Email - the most popular Internet tool, used to exchange messages between individuals
Mailing lists - which use email to enable communication among groups of people. Individuals send emails to the list email address and receive a copy of all emails sent to that address
Usenet newsgroup - a separate Internet system which allows users to read and contribute to global special-interest 'newsgroups'; the number of newsgroup topics is vast, and subjects range from the very dry to the totally bizarre
Computer conferencing - (sometimes also known as 'discussion boards' or more accurately 'threaded discussion lists') which enables groups of people to hold discussions by reading and posting text messages on a computer system. The advantages over mailing lists are that the messages are archived and the structure of the discussion is also recorded. Computer conferencing is widely used to support learning, and within the educational context is generally what people mean when they talk about 'CMC'
Internet Relay Chat (IRC) - an Internet system which allows users to chat 'live' (in real time) using text or audio Internet telephony, a way of using the Internet as an alternative to the main telephone network; currently in its teething phase, though exciting in that it has the potential to reduce the cost of calling long-distance to that of a local call
Videoconferencing - a means by which small groups of geographically distant people can hold discussions in real time, during which they are able to hear and see each other and share various other types of data.
Hybrid systems - systems such as WebBoard combine threaded discussion lists, IRC and email lists allowing users to switch easily between the two depending on the nature of the discussion. See also Yahoo Groups which is a free online service allowing you to set up a Web based email discussion list with optional forwarding to and replies from your normal email account. It also offers a facility to share documents and images.