A fief was the medieval term for a knight’s grant of land held in exchange for service to a lord.
In the feudal system, a lord could grant a fief to a vassal through a relationship involving obligations and protection. A knight might receive land, revenues, or rights over a particular estate, allowing him to support himself, maintain equipment, and provide military service when required.
A fief was not always a single farm or castle. It could include villages, rents, legal privileges, or other forms of income. The exact terms varied widely across Europe and changed over time, so historians use the word carefully rather than treating feudalism as one uniform system.
A fief should not be confused with a manor. A manor was an estate or local economic unit, while a fief described a grant held within a system of lordship and service. Some manors were fiefs, but the terms are not identical.