What's the difference between a primitive society and a medieval one?

I want to create a fictional world set in a medieval era with a lot of similarities with Europe in the Middle Ages, but with some foreign influences. The idea is to create a realistic world similar to our own in the Middle Ages, but with some magical aspects and unique cultures. I am going to ask for some advice on different matters relating to this world.<br><br>The first question is: what's the difference between a primitive society and a medieval one? How can a society progress from one to the other? Because I can imagine that during the dark ages after the downfall of an ancient civilisation, they can easily fall into chaos and become primitive, savages, or hunter-gatherers. How can they transition from that stage to a medieval one and what are the key steps for that to happen? I'd love to hear your thoughts on the matter.<br><br>Many thanks.