Arrakis, also known as Dune, is a desert planet in Frank Herbert's Dune universe. Dune is the most valuable planet in the universe because it is the only planet where the spice melange is found.
In humans, incidental exposure to spice or consumption of spice over time can have narcotic effects and cause minor physiological changes, most notably blueing of the eyes. Heavy exposure and conditioning combined with bioscience may cause major physiological and mental changes that allow some humans to become navigators capable of folding space for faster-than-light travel and communication, or others to become mentats, human computers.
Thus Dune and its spice make Interplanetary civilization and the galactic empire possible. It also makes Dune the site of longstanding economic, political and outright military power struggles between guilds that control space travel and trade, smugglers, dukes and barons of noble houses, the emperor, and Dune's indigenous people known as the Fremen.
Dune is the third world orbiting the star Canopus and has two moons.
Arrakis is more or less based on the Arabian Peninsula, including the desert environment and the culture of the Fremen people, who practive a pseudo-Islamic religion and live a tribal/nomadic lifestyle.