Well, the invention of electricity for example. Or, hey, that diminishing role of the church in every day life and the increase of secular institutions like science and stuff. Or the lack of, y'know, kings over large parts of the world. Or the fact that we have more than three continents now.

And that's just talking about someone from Europe or the Middle East. I imagine it would even weirder for someone from thirteenth century Africa or North America.

Um.

I'm sorry, the question is like asking what changed between the Bronze and Middle Ages, except even more so.