Farmers who were tied to the land during European feudalism. They were not slaves because they could not be bought or sold, but they could not readily leave the manor either. Serfs were given land to farm in exchange for service to their lord. This service usually involved working the lord's fields, maintaining roads and the manor, and providing military service in times of war. Serfs paid taxes to their lord in the form of crops. This is also how the paid the fee to use the manor's mill or other services.