Warning: Wikipedia contains spoilers
Flynn, a computer game programmer, is absorbed by being "digitized" into a digital world tyranically ruled by the "Master Control Program". Flynn's program is named "Clu". CLU is an old programming language. Flynn fights against a despotic Master Control Program to free his company's mainframe. He needs to find "Tron", a security program created by Alan that can help him escape to the real world. (The Tron program is also played by Boxleitner, whose character created it.) In the process, he has to participate in several action games such as the famous "LightCycles" game (the players' cycles leave an impenetrable barrier behind them which is used to trap opponents; Tron invented the LightCycles). In these games, the players represent different computer programs (or, more accurately, processes) who resemble their users.
Tron was one of the first movies to use long computer generated sequences, all in all, about 30 minutes of computer generated animation (blended with the filmed characters) were used. Though the plot has been criticized as being shallow, the movie is therefore celebrated as a milestone of computer animation. (The film, however, contains less computer-generated imagery than is generally supposed: many of the effects that look like computer graphics were created using traditional optical effects; The live action inside the computer was filmed in black and white, and colorized later with photographic and rotoscopic techniques.)
Although the film was initially unsucessful, the movie inspired several computer games, including a popular arcade game which produced more initial earnings than the film and made it a cult favourite. Disneyland also has a ride inspired by the film. The popular 1990s computer animated television series, ReBoot apparently was inspired by this film.
On August 25, 2003, a computer game sequel created by the original creators was released titled Tron 2.0. It is a first person shooter game where you play Jet Bradley, the son of Alan Bradley, who finds himself digitized and forced to battle menaces in the computer, both on his own and in a Lightcycle. It was hinted that if Disney judged the game to be successful enough, a feature film version of the sequel may be produced.