How is capitalism different from ancient or medieval economic system?

I think I generally have a good understanding of what capitalism is or how it functions. But I don't think I really understand what "capitalism" is in comparison to any other economic systems of the antiquities and medieval societies prior to capitalism.

Surely they had money and surely they had some system based on loaning and crediting assets and money. And utilizing these systems to function exchange of goods in markets and real estate.

So then, how is capitalism different from these ancient economic system? How is the modern sense of the word "capitalism" different from ancient or medieval systems?

TIA