18. A market is where buyers and sellers exchange goods and services.
Once your students have begun their communities and began trading resources, they can actually create a marketplace. It would be ideal if the marketplace could exist between the communities living in the world. The marketplace should be in a centralized location. Different communities could have specialties of what goods/resources they provided and took to the marketplace. Students could come up with a common form of “currency” that all items are worth. They could establish someone to handle the “currency” and the dealing out of goods/resources as needed. There could also be trades for certain items as well. The student who has collected enough wood to make a wooden pickaxe could turn in the wood needed and in return get their wooden pickaxe.