Feudal society is a military hierarchy in which a ruler or lord offers mounted fighters a fief medieval beneficium , a unit of land to control in exchange for a military service.
However, if this did not work, they could join a band of outlaws.
A feudal contract was an exchange of pledges established by custom and tradition that created the economic and political relationship between lords and vassals, or lesser lords.
What makes a contract legally binding? It was no fun to be a lowly serf in the feudal system.