system
Given the following post, respond as if you're commenting on Reddit:
human
What is "The Culture"

In the who would win subreddit I keep hearing about an overpowered group called The Culture. Who are they?
gpt
In universe, they're an anarcho-socialist space-based society, primarily human and near-human, and nominally run by "Minds" - extremely advanced synthetic life forms, that usually take the form of the multiple-kilometres long ships that the majority of the Culture's human and Drone population live on. 

They have a population well into the billions (trillions, possibly) and maintain one of the highest levels of technology in the Galaxy. The most telling thing is the motto most other civilisations have regarding them: "Don't fuck with the Culture". Although they look like peace-loving hedonists, their Ships can be utterly beyond ruthless when it comes to defending or avenging Culture citizens. 
  
  
Out of universe, they are the subject of the Culture novels by Iain M Banks. Try Excession as a good intro to the universe.