Dastans had no official religious or social purpose within their culture, and therefore no externally prescribed form. They existed for the sheer pleasure of the story-telling experience: created by the narrator’s artistic authority, they were sustained by the listeners’ responsiveness, by the perpetual question, ‘Then what happened?’ Dastan-narrators drew on the revered national verse epic Shāh nāmah (The Book of Kings) (c1010), and incorporated into its framework folk traditions of all kinds, creating narratives that were swept along by the strong currents of the imagination. Their ultimate subject matter was always simple:”razm o bazm,” the battlefield and the elegant courtly life, war and love.

Translated by Frances W. Pritchet, Read the complete text here..
http://www.columbia.edu/itc/mealac/pritchett/00litlinks/hamzah/index.html