A temporary place with long-term commercial value
At a major fair, buyers could compare multiple sellers in one place while merchants could meet customers, agents, financiers and other traders without travelling individually to every potential buyer.
The Metropolitan Museum notes that the Champagne fairs offered goods from widely separated regions, including Flemish cloth, Chinese silk, Egyptian satin, spices, northern furs and Russian wax.
The fair disappeared when the event ended, but the relationships did not. Orders, debts, contracts, price information and contacts travelled onward with the merchants.
See The Met's chronology of medieval France