Basically this is the difference:
For Primary Epic
No single author (each is a product of the oral tradition)Written down after centuries of oral transmissionSecondary Epic A single, gifted poet such as Virgil or Milton composes a work that imitates a folk epic. The Æneid and Paradise Lost, for example, involved considerable research and have the style of earlier epics (particularly in setting, dignified speeches, and extended similes.
