(FORTUNE Magazine) – When Vice President Al Gore discusses one of his favorite subjects, the so- called electronic superhighway, he calls up images of a country connected by computer terminals. The backbone of such a system, in fact, already exists: More than ten million people trade information via Internet, a network originally developed by the government that now connects libraries, college campuses, research labs, businesses, and homes, often using phone lines. Now AT&T is introducing a kind of Yellow Pages for Internet to help computer users find the data they want. Until now, they had to know exactly where to find information they needed or use specially designed software to dig it out. Researchers and academics who exchange E-mail, data, and technical information still form the majority of Internet users, although business users have helped traffic grow. The most traveled portion of the system: the National Science Foundation's NSFNet, which carried 26 billion packets of information last February, vs. ten billion in September 1991 (see diagram). The NSF, a government agency, expects Internet's capacity to triple by the end of 1994.