What is Discworld in the novel, Mort?

Discworld is a flat world that rides on the back of four giant elephants, who in turn stand on the shell of an enormous star turtle, Great A'Tuin. Discworld (often shortened to Disc) is a medieval place, where little kingdoms war, intermarry, and ally. Magical forces cause light and darkness to spread slowly over Disc's surface. Those who wander over the edge are lost.