Virtual -- an adjective that refers to objects, activities, etc., that exist or are carried on in cyberspace. For example, on the world wide web, you can find virtual or electronic malls and storefronts.

Virus -- an executable code that infects or attaches itself to other executable code in a computer in an effort to reproduce itself. The code must run for it to do damage to the system. Some computer viruses are malicious, erasing files or locking up systems; others merely present a problem through the act of infecting other code.