Manorialism (Seigneurialism) is the name for the organization of the economy in the Middle Ages in Europe. The economy relied mainly on agriculture. Manorialism describes how land was distributed and who profited from the land.
A lord received a piece of land, usually from a higher nobleman, or from the king. When he received the land, he also received all that was on it. That means that most of the people that lived on the land also belonged to the nobleman. The people, called peasants, had to pay to the lord, or they had to work for him. This way, the nobleman could live and support his family from what he received from the peasants. He had also certain legal powers, like that of a police force. The peasants were commoners or subjects and had to pay tribute to the lord. In return they received protection.