A more thorough explanation:

Definition: A fief is a piece of land that is given to someone in exchange for their loyalty and service. In medieval times, lords would grant fiefs to knights who would then become their vassals. The vassals would then owe the lord military service and other duties.

Metaphorically, the term fief can also refer to an area of control or influence, especially in a corporate or governmental setting. For example, a CEO may have a fiefdom within their company, where they have a lot of power and influence over a certain department or area of the business.

Examples:

• In medieval Europe, a knight might receive a fief in exchange for pledging loyalty to a lord and serving in their army.
• A powerful politician may have a fiefdom within their party, where they have a lot of influence over certain policies or decisions.
• A successful entrepreneur may have built a fiefdom within their industry, where they have a lot of control and influence over the market.

These examples illustrate how a fief can refer to both a physical piece of land and a metaphorical area of control or influence. In each case, the person who holds the fief has a certain amount of power and responsibility, whether it's to serve in an army or to make important business decisions.