Unlike most computer terms, "cyberspace" does not have a standard, objective definition. Instead, it is used to describe the virtual world of computers. For example, an object in cyberspace refers to a block of data floating around a computer system or network. With the advent of the Internet, cyberspace now extends to the global network of computers. So, after sending an e-mail to your friend, you could say you sent the message to her through cyberspace. However, use this term sparingly, as it is a popular newbie term and is well overused.
The word "cyberspace" is credited to William Gibson, who used it in his book, Neuromancer, written in 1984. Gibson defines cyberspace as "a consensual hallucination experienced daily by billions of legitimate operators, in every nation, by children being taught mathematical concepts... A graphical representation of data abstracted from the banks of every computer in the human system. Unthinkable complexity. Lines of light ranged in the non-space of the mind, clusters and constellations of data" (New York: Berkley Publishing Group, 1989), pp. 128.