Who was Aslan?

Aslan is a lion, King of the Beasts, and the son of the Emperor-Beyond-the-Sea. He rules over many countries, including Narnia, and the White Witch is frightened of his power. The animals of the forest all know who he is, though not all of them know him personally. Aslan is good, just, and forgiving, as is shown by his actions following Edmund's betrayal. Aslan is also a teacher: he engages Edmund in a conversation (presumably about morality) that Edmund is never able to forget, teaches Peter military strategies, and helps Lucy and Susan to learn from his actions when he dies in Edmund's place. He provides the children with an alternative to the education that they receive in their schools.

It is important to note that Aslan is fashioned as a Christ-like figure: he dies in Edmund's place, with the faith that he will come back to life. He knows that he will return to life because of the deep magic from before the dawn of time, but nevertheless fears the physical pain that he must endure. In the end, Aslan triumphs over the White Witch.