The Exceedingly Great Reward

In Genesis 15, God tells Abram of an exceedingly great reward. Also in this chapter, we see Abram being justified by faith and a mysterious event happens in which he cuts animals in half, falls into a deep sleep, experiences horror and darkness, and sees a smoking oven and flaming torch pass between the pieces. What is this about, what is the reward, and what lessons does it have for us today?