City Net is very similar to the Internet back before The Virus hit. When the Techno's invade The City, they implement City Net in order to lure people into complacency and so that they can start playing The Game.
City Net was especially welcomed my Sammy and Mouse, and all watched its first appearance - a Virtual Reality match between Lex and Java. When Lex loses, it becomes clear that Ram is certainly evil, and that he could easily have Lex wiped out.