Cybersex, computer sex or net sex is a virtual sex encounter in which two or more persons connected remotely via a computer network send one another sexually explicit messages describing a sexual experience. It is a form of role-playing in which the participants pretend they are having actual sexual relations, by describing their actions and responding to their chat partners in a mostly written form designed to stimulate their own sexual feelings and fantasies.
It sometimes includes real life masturbation. The quality of a cybersex encounter typically depends upon the participants' abilities to evoke a vivid, visceral mental picture in the minds of their partners. Imagination and suspension of disbelief are also critically important. Cybersex can occur either within the context of existing or intimate relationships, e.g. among lovers who are geographically separated, or among individuals who have no prior knowledge of one another and meet in virtual spaces or cyberspaces and may even remain anonymous to one another. In some contexts cybersex is enhanced by the use of webcams to transmit real-time video of the partners.
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The relative anonymity of Internet communication may provide encouragement to pedophiles (or, more commonly, ephebophiles) to seek out underage cybersex partners. In the course of such conversations, such individuals sometimes try to send child pornography to others or arrange real-life meetings (see child grooming). Such anonymity allows one to pose as any age or sex.Note:
Ephebophilia is the attraction of older individuals to adolescents, a phenomenon generally not assigned a separate term in most cultures unless it is between adult males and adolescent boys.
More at link:
http://en.wikipedia.org/wiki/Cybersex