Peasants' Revolt
Serfs were tenant farmers who worked without pay for a lord.  In exchange, they got permission to live on the lord’s land.  They also got protection from the knights living on the lord’s manor.  Under feudalism, serfs had many difficulties.  They barely had enough food to live on, and they had few possessions.  They were not slaves, but they were not completely free.  Serfs had less than any of the other social classes in medieval society.