What are three reasons The Canterbury Tales were and are important?

Chaucer's The Canterbury Tales are important for a number of reasons. First, they provide a comprehensive overview of life in the Middle Ages. Because Chaucer's pilgrims come from different social classes, modern readers learn a great deal about life in medieval England. In the cross-section of society that he provides, we meet pilgrims classified by those who pray, those who labor, and those who fight. We learn what their lives are like and what they value. Because Chaucer the pilgrim, or the narrator, passes judgment on them, we also see a social commentary that exposes their vices as well as their virtues.

The Canterbury Tales are also important because Chaucer, who certainly knew Latin, the language of the Church, and French, the language of literature, chose to write them in the common man's Middle English. Because he selected Middle English as the language for the Tales, he made the stories more accessible to the readers of the time. He also made English itself more acceptable and popular, leading other writers to adopt it as their language of choice. This makes Chaucer's stories almost singularly responsible for the adoption of English as the new language of literature in England.

Finally, Chaucer's framework for the stories adds a great deal to our understanding of the people of the medieval times, in terms of their literature, their folklore and even their values. The frame of the pilgrimage to Canterbury lets us know the significance of Saint Thomas Becket at the time. The use of the contest to elicit stories from the pilgrims is masterful because it allows the work to be read as an anthology. Here we see not only the cross-section of the pilgrims, as noted earlier, but also a cross section of the genres that were popular at the time, from the nun's priest's beast fable, to the Wife of Bath's romance, to the Pardoner's sermon to the monk's tragedy. 

The Canterbury Tales, then, are a unique representation of the time it describes, educating readers about the social distinctions and the literary interests of the Middle Ages, all while establishing English as the literary language of choice.