Both Everyman and Piers Plowman are medieval allegories dealing with religious and moral instruction. In Piers Plowman, the narrator has a series of dreams relating to how to live a Christian life according to the rules of the Catholic Church. He meets a series of allegorical figures, such as the wicked Lady Mede, who represents worldly corruption, and Conscience, whose name reflects his function within the allegory. Everyman sports similar allegorical figures, dealing with the individual soul's temptations and virtues. Like Piers Plowman, the characters in the drama tend to have on-the-nose names such as Death and Discretion.
Both plays also deal with preparation for the afterlife. According to medieval Christian theology, only good deeds and faith in Christ can lead an individual to heaven after death. The two plays feature the allegorical figures either helping or hindering the protagonists on their respective quests to attain a state of grace.
There are a few differences between the two works. Piers Plowman has more of a satirical bent in its depiction of society. Everyman lacks this comedic edge and has a more earnest tone. Piers Plowman is also much more political in nature, invested in the idea of a just society on earth as well as finding salvation in the life hereafter. Everyman is only interested in the second of these.