If you give me loyalty, I will give you 25 acres of this land.
Look at all this land! You've got yourself a deal!
During the Middle Ages, the poverty-stricken civilians had no army to protect them, and barbarians continued to invade and create conflicts.
At the time of the Middle Ages, there was another civilization known as Byzantium. They had just about finished the "Hagia Sophia".
Feudalism was an act of giving land to a lesser civilian of yourself in exchange for loyalty towards you. And from the civilian that you gave land to can give land to an even lesser civilian in exchange for loyalty towards himself.
The Church was the center of life in the Middle Ages. The Church dictated how people lived.
Many people never bathed, so people were sick almost all the time. These diseases spread very quickly.
Farms were 90% of the population. And in most of the farms, the harvests were poor.