The social structure is based on the feudal system which has fixed stages of wealth and power. Majority of people in the social structure in the medieval time were peasants, up to 90% of people were peasants. That leaves only 10% of people to be nobility and royals. The royals were the highest based stage on the social structure. The royals included kings, queens, princes and princesses . The kings were the highest authority in the land, the king's job was to take care of citizens in his kingdom. The queens played an important role in the medieval class system, queens were normally second in command to the kings. After the royals the nobles were the most powerful class in the social system. The next stage down after that is the knights. The main job of the knights were to protect the royals and the army. Right at the bottom of the feudal system was the peasants. People who were classed as peasant had the right to work land for the lord, serfs had no rights and other people who were slaves were bought and sold.
http://www.thefinertimes.com/Middle-Ages/social-classes-in-the-middle-ages.html
http://www.thefinertimes.com/Middle-Ages/social-classes-in-the-middle-ages.html