The key component of feudal society in medieval Europe was the hierarchical structure based on land ownership and the mutual obligations between lords and vassals. Lords owned large estates and granted parcels of land, called fiefs, to vassals in exchange for military service and loyalty. This system created a network of allegiances, where lower-ranking nobles and serfs were obligated to serve their lords. The feudal contract was central to maintaining order and providing security during a time of instability. Additionally, land was the primary source of wealth and power, influencing social status and relationships in medieval society.