The most usual way of looking at class in The Canterbury Tales is to split the pilgrims into the following four social classes:
First, and most numerous in terms of the people in the work, is the middle class. This class is made up of people like the Merchant, the Man of Law, and the Wife of Bath. These are people who were not born to wealth or position but who have acquired it. They are the upwardly mobile people of the time.
Second, we have the peasants. These are the low end of society. Examples include the Plowman and the Yeoman.
Third, we have the nobility. These are the social elite of society in Chaucer's time. The Knight and the Squire are the examples of this class.
Finally, there is the clergy. There are actually distinctions within the clergy, but they are generally talked about as one social class. The clergy in this work include the Prioress, the Monk and the Nun.