Most of the novel is set on Arrakis, a desert planet known as “Dune” and inhabited primarily by sandworms and a martial people called Fremen. The planet is the place of exile for Paul Atreides and his family, and was intended as a place of hardship. Paul, however, finds the Fremen admirable for their courage and faithfulness. They provide Paul with a useful fighting force; the Fremen are tough, fanatical fighters, unmatched by any others in the empire.
Except for walled-off regions, the planet is a sea of sand and rocky islands. To cross the sand is to risk being engulfed in vicious windstorms or swallowed by the gigantic worms that plow beneath the surface, sometimes rising to devour an unwary victim. The Fremen warrior code includes the practice of mounting a moving sandworm and riding it across the desert, a dangerous practice that Paul masters to prove himself to the Fremen.
The Emperor has miscalculated by sending the Atreides family to Arrakis. Its Fremen give Paul military power; its worm-produced spice, melange, is essential for space navigation, and control of the spice trade provides Paul with economic power. Much of Dune is about Paul’s clever use of the bleak planet’s resources.