Pornographic
material that appears to depict children, but
doesn't really. The use of the term "virtual," with its connotations of
"virtual reality," tends to mislead some people into thinking that
virtual child porn necessarily involves the Internet in some way, but it
doesn't have to.
There are two kinds of virtual child porn (or three, depending on how
you count):
1. Composites. The "models" in these pictures appear underage, and they are presented as such in the surrounding
text, in advertisements, etc. The models, however, don't really exist:
they were "assembled" from perfectly legal photographs using Photoshop
or some similar program (say, by pasting the head of a 10-year-old onto the body of a flat-chested 20-year-old). Thus, the creation of this kind of pornography
didn't involve children at all (one can argue that this sort of porn
prompts child abuse, but that's a separate debate).
2. Pictures of people who appear to be under the legal
age (and the surrounding text depicts them as such), but are actually
legal. In this case, the pornographer has simply found an 18-year-old who
looks 15 (or whatever).
In a recent United States Supreme Court decision (Ashcroft v. The
Free Speech Coalition), the Supremes held that these two forms of
pornography were protected by the First Amendment.
The term does not include pictures of women who appear to be under the legal age, but are actually over 18 and are described as such in the text. As far as I know, this sort of pornography has always been
legal--it appears in men's magazines like Tight, Hawk, Live Young Girls, and (sort of) Hustler's Barely Legal. It does tend to freak people out, though (myself included, sometimes). Supposedly, UK Customs briefly refused to allow magazine distributors to import Tight from the US because they could not believe that the models were of age. They only relented when the importers presented the customs inspectors with copies of the models' photo IDs and birth certificates.