What is the name of the social system in Medieval Europe?

During the Medieval Period in Europe, most countries (or kingdoms) functioned under a system of social stratification known as feudalism. The feudal system was favored because it was considered to be a simple, God-ordered way of organizing society. In a feudal kingdom, the king owned all of the land but broke it up into parcels to be governed by nobles in exchange for military service. The nobles then further divided the land to be worked by peasants who lived on smaller plots. The peasants received the protection of their local noble in exchange for their labor, which fed the noble and helped run his estate. 
For much of the Medieval Period, this system worked. Society functioned in three distinct Orders who worked to serve and protect one another. The king and nobility made up the bellatores, or "those who fight." The peasantry made up the laboratores, or "those who work." The third order, oratores, was made up of clergymen and monastics- "those who pray." The religious communities of the time received protection from nobility, sometimes food or labor from the peasantry, and in turn they prayed on behalf of the other two Orders of society.
Over time, the feudal system became increasingly convoluted as nobles might break up their land between lesser nobles, or even be obligated to a higher noble themselves! What's more, these kingdoms were often fighting one another, and peasants were an easy target for an attacking army. In addition to not receiving adequate protection from their nobles, many peasants struggled in times of crop failure. These poor farmers were often blamed for poor crop yields and were expected to maintain the amount of food given to the nobility while they may have starved in their own homes. Peasant riots were one of the contributing factors to the breakdown of the feudal system.
 
https://www.britannica.com/topic/feudalism