Araf is the Muslim sheol or borderland between heaven and hell for those who are, from incapacity, neither morally bad nor morally good.
Araf is also a partition. Between hell and paradise there is a high wall, an a'raf. On this partition stand men who have escaped from hell but who are not (yet) permitted to enter paradise. They yearn to enter paradise, but their sins and virtues are evenly balanced.