Since the Canterbury Tales prologue presents a cross-section of medieval society, we can learn much about the daily lives of the people, the various classes, and social issues.
We learn, first of all, about the three divisions of medieval society--fuedal, town, and church--and the characters associated with each. We learn about the ways various characters dress--the short tunic of the young squire, which attracts the ladies; the fur-lined coat of the monk, which indicates his wealth and his secular hobby hunting; the red stockings of the Wife of Bath, revealing her wealth (Dye was expensive). We learn also that overweight bodies (such as the Nun's and the Monk's) were a sign of wealth and privilege.
We learn more about various occupations. The Pardoner, for instance, sold fake relics to those searching for a place in heaven. The Summoner's job was to bring sinners to answer to the Church. The Guildsmen, had suddenly become rich through a sudden demand for their skills, as a result of the plague wiping out one-fourth of population. Physicians profited from the plague as well as from kickbacks from apothecaries.
We learn that medieval society was plagued by hypocritical church officials (for example, the Monk, Friar, Pardoner) who enriched themselves by preying on the poor and vulnerable. We learn that not all who worked for the church were truly pious, and that many were quite corrupt and heedless of their vows of poverty, chastity, and devotion. But we learn that those outside the church could also be corrupt. A street-smart Manciple could outsmart book-learned lawyers. A Miller can easily increase his profit by putting a heavy thumb on the scale. A Merchant could dress in finery but actually be in debt up to his eyeballs. An unsavory Skipper might execute his prisoners. An otherwise skillful Cook might have an oozing sore.
But then we learn also that virtue could be found in Medieval society. Some scholars, such as the Oxford Cleric, loved to learn and teach; some preachers led by example, such as the Parson; decent farmers, such as the Plowman, might lead humble and compassionate lives; hospitable Franklins might offer guests fine food and drink.
In short, we learn much about medieval society and much about our own.