An estate of land, especially one held on condition of loyalty and service, is known as a fief.
The term you're referring to is "fief." In the feudal system, a fief was an estate or piece of land granted to a vassal in exchange for their loyalty and service. This relationship was known as a feudal relationship, where the vassal, often a knight or noble, would receive a plot of land called a fief from a higher-ranking lord or monarch, known as a liege lord. The vassal would then owe certain duties and services, such as military support or financial dues, to their liege lord. The fief itself typically included not only the land but also the serfs (peasants) who lived and worked on the land.
