Han is explaining the history to Rey, who probably hasn't had much in the schooling let alone much history. But in the end they talking to the audience and IMO talking down to the audience.
Well the impression I get is that Rey and everyone else have heard the stories about what happened, and that those stories are pretty common knowledge. But the problem is that so much time has passed, and there is no way of proving any of it, that people have just accepted it as nothing but a legend or myth by this point.
Which I think is a really inspired idea, and does a great job restoring some of the wonder and mystery to the Force and the Jedi that was completely lacking in the prequels.