A more thorough explanation:

Villeinage is a historical term that refers to a type of feudal tenure in which a tenant held property through servitude to a feudal lord. The tenant was obliged to render base services to the lord, which could include agricultural work, carrying out tasks around the lord's estate, or other duties as commanded by the lord.

There were two types of villeinage: privileged and pure. In privileged villeinage, the services to be performed were certain, although they were still of a base and servile nature. In pure villeinage, the services were not certain, and the tenant was obliged to do whatever they were commanded whenever the command came.

For example, a tenant in pure villeinage might not know what work they would be doing from one day to the next. They might be required to thresh grain one day, dig ditches the next, and carry heavy loads the day after that. This uncertainty made the tenure unfree, as the tenant was not able to plan their work or their life with any certainty.

Villeinage was a common form of tenure in medieval Europe, particularly in England. It was gradually phased out over time as the feudal system gave way to more modern forms of land ownership and labor relations.