"I have not yet received information about what happened."
Translation:Mi ankoraŭ ne ricevis informon pri kio okazis.
Liken it to English: "About that which happened"; about that [thing] which happened.
But why are both correct? "...about that which happened." and "...about what happened"? They are very different.
The meaning is basically the same; I was talking about the grammar (?) or perhaps that is sentence structure. If it is both, is there a difference in use? If it is only one, which one and why?