All mandalas depict spiritual planes of reality. Tibetan Buddhism use them to map sacred abodes of the gods, Buddhas, bodhisattvas(aspiring Buddhas) and dakinins(skydancers), within which infinite wisdom and compassion are manifested. Some mandalas illustrate the obstacles that have to be overcome in order to cultivate compassion and wisdom; these are often depicted in the form of terrifying demons.
Another lovely ritual use of mandalas is the Tibetan practice of designing and creating elaborate sand mandalas, such as Kalachakra. Part of the purpose of this esoteric ritual is to demonstrate the impermanence of our present lives and physical condition. When monks wash away the beautiful and highly intricate mandalas that have taken many days to create, they believe that this dissolves the energy created through the spiritual practice and release its merit. By mixing the sand into rivers and oceans, this merit spreads through them and benefits the world.
Mandala patterns are also found in non-Eastern mystic traditions. Within traditional cultures, from Navajo to Tibetan, mandalas are used to help attune man's awareness to his place in a holistic world.