Cyber-Punk is a subgenre of science-fiction. Cyber-Punk stories are typically set in post-industrial dystopias (Tokyo is very popular) and feature either-
A. The wide-spread social effects of rapid technological change
B. A collection of computerized data that has become nearly omnipresent and omniscient.
C. Invasive modifaction of the human body or other natural biological systems.
E. All of the above.
I first learned about the Cyber-Punk sub-genre while doing research for a Psycho-Pass panel at this year's Seishun-Con anime convention (You can watch the first part below).
To me, one of the most interesting aspects of this sub-genre is the "Punk" part of Cyber-Punk. While just about all science-fiction stories feature human beings' reaction to scientific and technological changes, Cyber-Punk stories hone in on the reaction of rebellion and stretch the limits of their futuristic settings.
I've found that it really helps my creative process to understand the genre of a story that I'm trying to tell. My themes become more organized and I can see the context of how my work might fit in to the greater body of the storytelling world. To help focus a few of my creative projects, I've taken it upon myself to define a few era-based sub-genres that branch off of Cyber-Punk themes.
1. Dark-Age-Punk: Stories feature violent rebellions against socially accepted systems (feudal systems and unchecked monarchy) stretching the limits of low-tech peasant weapons (farming tools, bows and arrows, fire etc.).
Settings: Historical medieval or alternate historical medieval. Religious overtones are common.
Example Media: Robin Hood literature (especially Ridley Scott's vision).
2. Retro-Punk: Stories feature aggressive business advancements stretching the limits of available technology and socially accepted business practices.
Settings: 20th century or alternate 20th century. Worldviews are modernist.
Example Media: Halt and Catch Fire, MadMen, The Greatest Showman (if you squint).
3. Present-Punk: Stories feature social revolution against society itself, stretching the limits of present day ideaologies and technology.
Settings: Alternate 21st Century. Worldviews are postmodernist.
Example Media: Mr. Robot, Fight Club (kind of).