Geoffrey Chaucer's The Canterbury Tales is a story about a group of characters who travel from London to the shrine of the martyr Thomas Becket on a pilgrimage. Written in the fourteenth century, this narrative poem has maintained its appeal because of the detailed portrait it offers of so many different kinds of people from the Middle Ages. It is also the first major literary work to be written in English, although most people wouldn't be able to read it in its original form, Middle English.

Chaucer's realism in the prologue is based on his use of satire. Satire is the act of using humor to expose a weakness or problem in society. Chaucer's use of satire lends a realism to the poem that most works of his time did not engage in.

One of the most realistically drawn characters is the Pardoner. The Pardoner travels from church to church carrying with him fake religious “relics.” He charges unsuspecting parishioners money to view these relics, which really consist of a pillowcase (supposedly Mary's veil), a piece of ordinary fabric (supposedly a piece of Saint Peter's sail), and a jar of pig bones (supposedly the remains of an unnamed saint). He is so successful that:

he in one day got himself more money

than the parson got in two months

Chaucer's realism lies in his depiction of a church official as greedy and dishonest, making much more money through deceit than the honest parson could make.

Several other characters in the prologue are also satirized in a realistic fashion, among them the Doctor, Monk, Friar, Merchant, and Miller. 

What are some elements of realism in Chaucer's "Prologue" to The Canterbury Tales?

It's challenging to think of Chaucer's work in terms of realism, which is a nineteenth-century movement that values portraying things as they are, like describing an objective photograph. Henry James and Gustave Flaubert are relevant examples of realist authors.

Chaucer writes in the fourteenth century, and it's hard to imagine an audience being drawn to that type of story. Chaucer's reading audience was largely courtly, due to his own court connections and the illiteracy of many subsections of fourteenth-century England. (See this site for a qualification of literacy assumptions.)

Chaucer's Canterbury Tales is a collection of genres representing the variety of stories told in his day. He invents a vast array of social types to tell these stories, seemingly matching each tale to its teller. In the General Prologue, Chaucer the Pilgrim presents structural irony, which occurs when one has a naive narrator. This narrator thinks all the pilgrims are "worthy," yet, through the descriptions, we find a sliding scale of moral and social value. This irony creates the Estates Satire, a common medieval genre that satirizes people for trying to rise above or below their estate, or for not fulfilling the expected duties of the estate to which they belong. For satire to work, even in this broad comedy, some measure of realistic portrayal must occur. Chaucer deals in stereotypes, but he offers enough distinguishing detail for one to see the pilgrims as uniquely individual or realistic versions of type: the squire curls his hair, the Wife wears red stockings to church, and the Monk has bells on his horse.

Another subtle way that Chaucer may be nudging toward realism is through his matching of tale to teller—though in many instances we are not entirely sure who tells which tale. In the "Knight's Tale," however, we are certain that the speaker is a Crusade-battered fighter. He tells a conventional romance but struggles to do it well. He minimizes some elements (Theseus's wedding, or Emily, or pretty much anything that concerns human love, for instance) while emphasizing others (e.g., war, injustice, submission to duty). His view of life is distinctly dark, as seen in the description of the Temples, and he confuses Providence and Chance at significant moments. Many readers of this tale find common features associated with PTSD—not surprisingly, given his history at some of the bloodiest of the Crusades.

Similarly, the dissonance between the Wife's wildly brilliant and anti-misogynistic Prologue and her tale, which indulges in striking wish-fulfillment, suggests an odd gap that readers are invited to interpret. Like the Knight's own approach to the storytelling task, the Wife's offers elements that point in a very elemental way to a certain psychological realism.

These subtle qualities that reflect essential human foibles may be why Chaucer remains so delightful to read centuries later.

What are some elements of realism in Chaucer's "Prologue" to The Canterbury Tales?

With Realism as a representation of details from contemporary life, Chaucer's The Canterbury Tales is, indeed, realistic. 

• Chaucer's unprecedented use of the vernacular rather than Latin or French, as was hitherto employed in literature, provides much realistic detail and reflects the life of the pilgrims of the time. 
• Moreover, his presentation of an extensive view of society is a veritable tableau of fourteenth-century England.
• In the "General Prologue," Chaucer's very subject matter--a pilgrimage--is certainly realistic as religious pilgrimages were customary.

Then do folk long to go on pilgrimage,
And palmers to go seeking out strange strands,

• Details appertaining to the historical setting of the time are present as, for example, there is an allusion to the Black Plague and Thomas a Becket, who was martyred at Canterbury:

...they to Canterburywend,
The holy blessed martyr there to seek
Who helped them when they lay so ill and weak

• Finally, Chaucer promises to provide realistic descriptions of the pilgrims.

To inform you of the state of every one....
And who they were, and what was their degree,
And also what array they all were in;