You're thinking of villeins, or serfs, which were peasants who were tied to the land. The vassal-liege relationship (at least as it developed in Europe) was predicated on the King owning all the land and him essentially 'renting' it out to lords and knights in exchange for military service. Modern bureaucracies didn't develop until the early modern period, meaning the average monarch didn't have the personnel to administer huge tracts of land. He (or she) instead granted a portion to a lord, who became his vassal in exchange for agreeing to provide a mutually agreed upon period of military service. Lords then divided their own land and granted tracts of it to knights and lesser lords, who became vassals of the lord in the same manner the lord was vassal to the king. Peasants generally weren't regarded as people during the medieval period (unless they lived in a town with a charter), so they weren't vassals as much as property, but if you were a lord owing service for his (or her) land, the feudal system wasn't half bad. It should also be noted that kings could owe fealty to other kings - the Plantagenet kings of England did fealty to the kings of France for their French territories, while the kings of Scotland did fealty for English lands at different times. So yeah, if you were at the top of the social order in Europe during the Middle Ages you were more than likely someone's vassal and it was a pretty good arrangement as long as both sides upheld the feudal contract.