Final answer:
Lords granted land to lesser vassals or knights primarily in exchange for protection. Knights served their lords militarily and upheld justice within their land-holdings in support of feudal society's structure. This system was fundamental in maintaining social order and security in medieval Europe.
Step-by-step explanation:
Under feudalism, lords granted land, known as fiefs, to lesser vassals or knights in exchange for various services and obligations. The primary service that vassals provided to their lords in return for the fief was protection. Knights pledged to serve in the military forces of their lord, to protect the lord's territories, and maintain the peace as part of the feudal hierarchy.
In addition to military service, vassals also offered counsel, attended the lord's court, and upheld justice within their territories. The system was based on mutual support and obligations with the purpose of maintaining the social order and providing security.
The fief was an economic asset allowing the vassal to extract wealth from the land, usually through the labor of serfs, to support his military obligations. In return for their labor, peasants working the land received protection and a place to live, thus creating a deeply interconnected society defined by land ownership and the provision of safety and justice for its members.