A more thorough explanation:

Feudatory is a term used in history to describe a vassal who owes feudal allegiance to a lord. It can also refer to the grantee of a feud, or the tenant who held an estate by feudal service.

Every receiver of lands, or feudatory, was therefore bound, when called upon by his benefactor, or immediate lord of his feud or fee, to do all in his power to defend him. - 2 William Blackstone, Commentaries on the Laws of England 46 (1766).

For example, in medieval Europe, a lord would grant land to a vassal in exchange for their loyalty and military service. The vassal would become a feudatory, owing allegiance to the lord and providing them with military support when needed.

Another example would be the relationship between a king and his barons. The barons would hold land from the king and would be expected to provide military support in times of war. In return, the king would provide protection and support to the barons.

These examples illustrate the concept of feudalism, where land ownership and military service were closely linked. The feudal system was prevalent in Europe during the Middle Ages and played a significant role in shaping the political and social structures of the time.