system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] what does the standard citizen know about the galaxy?

Do normal citizens know about the various Xenos races, do the know there are a lot of marine chapters, or do they not even know about marines unless they are in a system with a marine homeworld? What other things do they know or don't know?
gpt
Depends on where they're from.

A feral worlder might know that the Sky-emperor's sons occasionally come to call for them and that it's a blessing to be chosen. Beyond that, nothing beyond surviving the night.

A Hive Worlder is probably aware of the existence of the Astartes in a vague stained-glass image or carved image of them kind of way. They'll probably never see one in the flesh, or a Xenos of any type for that matter. They'll know that distant, holy Terra is the throne world. Beyond that they'll maybe be familiar with their sector if they're in a line of work that involves shipping or trade. They're probably told boogey-man stories about the inquisition as kids.

The more focused planets, Agri-worlds, forge-worlds, would range between the two most likely. There's not an average imperial citizen who's gonna be like "Oh, that's an Eldar Aspect Warrior!" Or whatever anywhere.

The only way that the Imperium is able to keep itself together is by keeping the populace ignorant of things beyond their walls. If they do know anything about Xenos, it's probably sub "Imperial Infantryman's Uplifting Primer" levels of useful information. depictions of frail, wimpy Orks being crushed under the perfect, pristine boots of guardsmen in the town square statue and that sort of thing.