What purpose does the general Prologue serve?

The General Prologue was probably written early in the composition of the Canterbury Tales, and offers an interesting comparison point to many of the individual tales itself. THe Prologue offers useful or enlightening suggestions, but they are no means a complete, reliable guide to the tales and what they mean. What the General Prologue offers is a brief, often very visual description of each pilgrim, focusing on details of their background, as well as key details of their clothing, their food likes and dislikes, and their physical features. These descriptions fall within a common medieval tradition of portraits in words (which can be considered under the technical term ekphrasis), Chaucer's influence in this case most likely coming from The Romaunt de la Rose.