Cyberpunk is a subgenre of science fiction in a dystopian futuristic setting that tends to focus on a "combination of lowlife and high tech", featuring futuristic technological and scientific achievements, such as artificial intelligence and cybernetics, juxtaposed with societal collapse. Basically an advanced technology world inhabited by people who can't afford the luxuries. The structure of these novels would usually be powerful megacorporations and private security forces are on one side, and the seedy underbelly of illegal trade, gangs, drugs, and vice is on the other. Politics, corruption, and social instability are interwoven throughout all of this.
We can break down a basic definition of cyberpunk by dissecting the word itself. Cyber refers to technology or cybernetic enhancements to the body. But this can can also refer to other technologies such as biotechnology and nanotechnology for instance.
Punk, on the other hand, refers to the people and the attitude that cyberpunk has. Protagonists in cyberpunk tend to be outsiders, anti-heros, outcasts, criminals, visionaries, dissenters, and misfits.
One of the core cyberpunk authors that is generally accepted to have laid the ground work of the cyberpunk movement was William Gibson (Gibson is considered the founder of Cyberpunk). One of his most famouse cyberpunk works was "The Neuromancer".
“The future is already here — it’s just not very evenly distributed.” – William Gibson
Neuromancer is a cyberpunk novel about a group of mercenary criminals who secretly work for an artificial intelligence that's trying to break free. It is a novel deeply entrenched in themes of individual identity and relevance of physical human embodiment.