The social and political system of loyalties and land exchanges in medieval Europe is known as feudalism. This hierarchical system was characterized by land ownership and obligations among different classes, primarily kings, nobles, knights, and serfs. Lords owned large estates and granted portions of their land (fiefs) to vassals in exchange for military service and loyalty. Serfs worked the land for the lords and were bound to it, often living in servitude. This decentralized system facilitated local governance and protection in a time of relative instability following the fall of the Roman Empire, shaping medieval European society and economies.