The prologue gives a basic set up of the story.
General setting: the journey of 30 travelers from a small tavern (in a town near London) to Canterbury. The travelers are going to pay tribute to the shrine of St. Thomas aBecket. Along the way it is suggested that to pass time on the journey, each should tell a story. At the end of the journey, the best story will be chosen.
Characters: the narrator goes on to give a glimpse of each of these travelers who will be on the journey. This first description is brief and based largely on appearance and a few actions. Follow the link for a more in-depth list.