What was the basis of the feudal economy?

Feudal Economy is the the system where all land ownership belongs only to the King. This system was existed particularly in the time of middle ages, where only the King had all the land of that country/kingdom and only he could give land to whomever he thought worthy. Kings usually allotted the land to the noble and lords. Nobles and Lords were the people who fought on the king's behalf. Manors was the specific term used when king give the land to the nobles and lords. King occupied highest level in that system. The peasants or the serfs were at the very lowest part in that economy.