During the time that is known as the High Middle Ages, European society began to change. Up to that point, the society had been largely agrarian. During the High Middle Ages, the society became more urban. There was more commerce and trade that centered around towns than had previously existed. This change came about because of advances in farming.
In order to have towns and merchants and trade, farmers must produce food surpluses. Farmers as a group must produce enough to feed themselves, but also enough to feed all the people who live in towns and who do things like making cloth or trading or working with metal. Before the High Middle Ages, farmers were not able to do this. Beginning around 1000 AD, farming techniques improved. This came about because of such things as the invention of the heavy wheeled plow, which allowed more fertile land to be cultivated. It came about with the invention of collars that allowed horses to pull plows, which they could do more quickly than oxen could. Other factors helped as well.
As these advances occurred, farmers could produce greater surpluses. These surpluses allowed more people to become artisans, traders, and merchants. This development changed medieval life significantly.