Canterbury Tales is a collection of stories built around a frame narrative or frame tale, a common and already long established genre of its period. Chaucer's Tales differs from most other story "collections" in this genre chiefly in its intense variation. Most story collections focused on a theme, usually a religious one. Even in the Decameron, storytellers are encouraged to stick to the theme decided on for the day. The idea of a pilgrimage to get such a diverse collection of people together for literary purposes was also unprecedented, though "the association of pilgrims and storytelling was a familiar one". Introducing a competition among the tales encourages the reader to compare the tales in all their variety, and allows Chaucer to showcase the breadth of his skill in different genres and literary forms.
While the structure of the Tales is largely linear, with one story following another, it is also much more than that. In the General Prologue, Chaucer describes, not the tales to be told, but the people who will tell them, making it clear that structure will depend on the characters rather than a general theme or moral. This idea is reinforced when the Miller interrupts to tell his tale after the Knight has finished his. Having the Knight go first, gives one the idea that all will tell their stories by class, with the Knight going first, followed by the Monk, but the Miller's interruption makes it clear that this structure will be abandoned in favour of a free and open exchange of stories among all classes present. General themes and points of view arise as tales are told which are responded to by other characters in their own tales, sometimes after a long lapse in which the theme has not been addressed.
Lastly, Chaucer does not pay much attention to the progress of the trip, to the time passing as the pilgrims travel, or specific locations along the way to Canterbury. His writing of the story seems focused primarily on the stories being told, and not on the pilgrimage itself.