Computer Mediated Communication

Computer-mediated communication (CMC) is defined as any communicative transaction that occurs through the use of two or more networked computers^. While the term has traditionally referred to those communications that occur via computer-mediated formats (e.g., instant messages, e-mails, chat rooms), it has also been applied to other forms of text-based interaction such as text messaging. Research on CMC focuses largely on the social effects of different computer-supported communication technologies. Many recent studies involve Internet-based social networking supported by social software. (Wikipedia)

Some of the modes of CMC 

Email -  More formal in nature (language), alert (subsciption).
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems requires that the author and the recipient both should be online at the same time, in common with instant messaging. (Wikipedia)

IRC - Chat immediately/ instantly, Short form, acronym, emoticon (language)
Internet Relay Chat (IRC) is a protocol for real-time Internet text messaging (chat) or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file sharing. (Wikipedia)


Blog - A blog (a portmanteau of the term web log) is a personal journal published on the World Wide Web consisting of discrete entries ("posts") typically displayed in reverse chronological order so the most recent post appears first. Blogs are usually the work of a single individual, occasionally of a small group, and often are themed on a single subject. Blog can also be used as a verb, meaning to maintain or add content to a blog.

Online Chat - Online chat may refer to any kind of communication over the Internet, that offers a real-time direct transmission of text-based messages from sender to receiver, hence the delay for visual access to the sent message shall not hamper the flow of communications in any of the directions. Online chat may address point-to-point communications as well as multicast communications from one sender to many receivers and voice and video chat or may be a feature of a Web conferencing service.

Social Networking - A social networking service is an online service, platform, or site that focuses on building and reflecting of social networks or social relations among people, who, for example, share interests and/or activities. A social network service consists of a representation of each user (often a profile), his/her social links, and a variety of additional services. Most social network services are web-based and provide means for users to interact over the Internet, such as e-mail and instant messaging. Online community services are sometimes considered as a social network service, though in a broader sense, social network service usually means an individual-centered service whereas online community services are group-centered. Social networking sites allow users to share ideas, activities, events, and interests within their individual networks.

References

Blog. (2012). In Wikipedia. Retrieved May 25, 2012, http://en.wikipedia.org/wiki/Blog

Computer Mediated Communication. (2012). In Wikipedia. Retrieved May 25, 2012, from http://en.wikipedia.org/wiki/Computer-mediated_communication

Email. (2012). In Wikipedia. Retrieved May 25, 2012, from http://en.wikipedia.org/wiki/Email
         
Internet Relay Chat. (2012). In Wikipedia. Retrieved May 25, 2012, from http://en.wikipedia.org/wiki/Internet_Relay_Chat

Online Chat. (2012). In Wikipedia. Retrieved May 25, 2012, http://en.wikipedia.org/wiki/Online_chat

The Social Network. (2012). In Wikipedia. Retrieved May 25, 2012, http://en.wikipedia.org/wiki/The_Social_Network