Fuedalsim is this:
the dominant social system in medieval Europe, in which the nobility held lands from the Crown in exchange for military service, and vassals were in turn tenants of the nobles, while the peasants (villeins or serfs) were obliged to live on their lord's land and give him homage, labor, and a share of the produce, notionally in exchange for military protection.
Nobles are rich and peasant are poor there to different people in a period to different people in a food chain. This is not hard you can google the answer person