system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are there multiple variations/stories of the same super hero characters, and how do you know which storyline/universe you're following is the chronologically "correct" one?
gpt
Retroactive continuity, aka retcons.

They give a superhero an origin story, 30 years later they decide that story is too goofy/racist/dated, and they come up with some crazy time travel/doppelganger/alternate reality nonsense to explain, "Oh, well that didn't REALLY happen, what REALLY happened is ___."

Because this gets fairly confusing, comic universes occasionally "reset," using some extravagant plot device, and they basically start from scratch.  DC is particularly fond of doing this.

Comics from the same "run" should follow chronologically.