After Charlemagne died, the Frankish empire fell apart. Without the empire to keep things going, each part of the empire fell to fighting. With each city and state fighting each other, some way had to be found to end it. Feudalism grew out of the chaos. Feudalism was a way to get an army together quickly but it was more then that. It was a way of life.
Under the feudal system everyone served someone above them. The feudal system was based on a pyramid of vassals. A vassal meant some one who serves. At the bottom and making up most of the pyramid were the peasants. The next layer up were the knights. The next layer up were the nobles and officials. The King was at the peak, at the very top of the pyramid.