What is the difference between feudal system and the manorial system which prevailed in England during the period of William the Conqueror?
Both feudalism and manorialism were part of a broad and at times complex social arrangement in medieval society, not only in England but throughout western Europe.
Feudalism defined a relationship between a greater nobleman, commonly called the lord, and a lesser nobleman known as a vassal. It was sealed by a solemn ceremony in which the vassal pledged fealty (loyalty) to the lord in exchange for a grant of land, commonly known as a fief. The vassal owned the land in his own right together with any profits derived from it. His obligation of loyalty to the lord meant that he would not fight against him; and also would provide a certain number of days of military service fighting for the lord. The vassal might have vassals of his own who in turn were obligated to provide military service. The entire arrangement could be rather complex: many upper lords were vassals themselves and many vassals were lords to other vassals. Among the circumstances leading to the Hundred Years War, the king of England had pledged fealty and become the vassal of the king of France. After a particularly raucous disagreement, King John of England became the vassal of the Pope, and pledged the entire kingdom as the Pope's fief. It is important to note that all parties involved in a feudal relationship were members of the nobility. No commoner ever became a vassal.
Manorialism broadly describes the relationship between the lord of the manor (literally the "land lord") and the commoners, often peasants tied to the land known as serfs who lived on his estate. The manor itself was a part of the fief granted to him by his lord. The commoners did not own the land, but rather rented it from the lord. They did not pay money rents, but rather owed him a portion of their crops and were also obligated to perform work on his roads, mills, etc. Their obligation to work normally consisted of a set number of days per week. In addition to the services of his tenants, the lord was entitled to a fee for anyone who used his roads, bridges, or mills. He also was judge and jury for any disputes which arose on the manor.
The beginnings of Feudalism can be traced in Western Europe from the decline of the Roman Empire, but its political and social organization became firmly established after the fall of Charlemagne's Empire during the Early Middle Ages. The word derives from the Latin feodum, meaning "fief" and from a Germanic word meaning "cow," the concept being one of valuable movable property. The fiefdom on which the serf labored and which the lord protected and the bishop evangelized remained as a political, social and economic entity unto itself.
Although related, Manorialism was based strictly on social and economic concerns where peasants held the land they labored upon in return for payment of produce or money rendered to the lord of the estate. There was no relationship between the manorial system and the political and military structure of the related feudal system. The Manorial system was prevalent in Europe and similar systems existed outside Europe as in Japan and India.