The list of advances
Feudalism is the political system revolving around the three key concepts of lords, vassals and fiefs.
It is a prerequisite of chivalry.
In the unsettled times that followed the collapse of Charlemagne's Frankish empire, a new social and political system arose in Europe, called Feudalism. Derived from the concept of Monarchy, it was a hierarchial system where each succeeding stratum owed allegiance to those above. At the bottom were the serfs, who worked the land for the lord of the local manor. The local lord in turn managed the land for the lord above him, and so on to the king, who actually owned all the land. The people at the bottom of the hierarchy were protected by those above, and in return served their masters. Feudalism led to the code of Chivalry and the mounted Knight.