"Retconned" is a portmanteau (a blend of two words) of "retroactive continuity."
In serialized fiction (like comic books, TV shows, movie franchises, or long-running novels), a "retcon" means a new piece of information is introduced that changes, contradicts, or recontextualizes previously established plot points, character histories, or world-building elements.
Essentially, it's going back and altering the past of the story without actually changing the previously published material. The audience is simply expected to understand that the "new" information is now the "true" history of the fictional world."
...Star Wars has absolutely been retconned, and quite extensively! It's a hallmark of the franchise, both intentionally and unintentionally, across its long history....
for example, ...Darth Vader being Luke and Leia's father/Leia being Luke's sister: This was a massive retcon from the initial conception of A New Hope, where Vader was just a villain and Leia was a separate princess. This twist in The Empire Strikes Back and Return of the Jedi fundamentally reshaped the saga..."
