This is part of the Medieval European History Metanode.
There were four basic elements of feudalism:
Personal Relationship
This was known as the "vassalage". It grew out of the relationships between the potentates and comitatus of the late Roman era (see the fall of the Roman Empire). Both the vassal and the lord were of the noble class. One became a vassal through a ceremony of commendation: the vassal declared his homage, plead an oath of fealty, and exchanged a kiss with his lord. This was a legal act of placing oneself under another person's authority. The vassal pledged 40 days of military service each year, and received protection and economic support from the lord in return.
Property Element
The vassal also received property, also known as a "benefice" or a "fief". Early in the history of feudalism, the vassal was tied to his fief at commendation. The Carolingians handed out fiefs in order to strengthen support for the government. Fiefs later became hereditary; the heirs of the vassal were expected to be offered the opportunity to pledge commendation to the same lord. This became law under Charles the Bald with the Capitulary of Quierzy in 877. Not much later, we see evidence of the first instance of a plurality of lords: one vassal pledged fealty to several different lords, creating quite a brouhaha when the lords wanted to fight against one another.
Possession of a Horse
Horses were a necessary element of warfare in the Middle Ages; they were the heart of the feudal army, and vassals were expected to be knights. Horses were very expensive in those days. The war horses were very large, comparable in size to the Clydesdale horses of today (unlike the horses you see in most movies about knights, which are far too small to carry all of that armor). The lords gave their vassals a horse for the purpose of warfare.
Private Possession of Governement Powers
Through feudalism, the lords eventually took powers once reserved for kings. They held armies, administered justice, imposed law, and held court. The monarchs of France took advantage of feudalism to keep their nobles from having such power by granting fiefs themselves.