A more thorough explanation:

Definition: A vassal is a person who is granted a fief, feud, or fee by a lord in exchange for loyalty and military service. In other words, a vassal is a feudal tenant.

Example: In medieval Europe, a lord would grant land to a vassal in exchange for the vassal's loyalty and military service. The vassal would then become responsible for managing the land and providing soldiers for the lord's army.

Example: An arriere vassal is a vassal of a vassal. For example, if Lord A grants land to Vassal B, and Vassal B grants a portion of that land to Vassal C, then Vassal C is an arriere vassal of Lord A.

These examples illustrate how vassals were an important part of the feudal system in medieval Europe. They were granted land and protection by their lords, but in return, they had to provide military service and loyalty. The concept of vassalage helped to maintain the social and political order of feudal society.