Final answer:
Vassals were wealthy landowners who received a fief from a king for their loyalty and obligated to perform services, primarily military. Serfs worked the land and were bound to it without full freedom. The feudal system created a strict hierarchical society based on this land ownership and protection.
Step-by-step explanation:
Vassals were wealthy landowners who received land, or a fief, from a king in return for loyalty. The feudal system was primarily a protection-oriented structure, wherein lords and kings granted lands to warriors or vassals in exchange for military service or pledges of support. This service included actively participating in defense and warfare, advising the lord, and serving in his court. Overseeing the work of the serfs, who were bound to the land and responsible for its cultivation, became part of the vassals' duty. The serfs, on the lower rung of the social hierarchy, were neither slaves nor entirely free and had to accept the abuse and demands of the lord in charge of the fief they worked on.