Ogoh-ogoh are statues built for the Ngrupuk parade, which takes place on the eve of Nyepi day in Bali, Indonesia. Ogoh-ogoh normally have form of mythological beings, mostly demons. As with many creative endeavours based on Balinese Hinduism, the creation of Ogoh-ogoh represents spiritual aims inspired by Hindu philosophy.
The main purpose of the making of Ogoh-ogoh is the purification of the natural environment of any spiritual pollutants emitted from the activities of living beings (especially humans). The forms of Ogoh-ogoh represent the Bhuta-Kala (Bhuta: eternal energy, Kala: eternal time), according to Hindu teachings. The imperceptible potentials of nature cannot be thoroughly explored by anyone. Philosophically, civilized men are required to manage the natural resources without damaging the environment itself.
Aside from being the symbol of Bhuta-Kala, Ogoh-ogoh is considered a symbol of modes of nature that form the malicious characters of living beings. Each village usually build one Ogoh-ogoh mainly built by each village's Seka Truna Truni (Balinese village's youth organization), but often some smaller ogoh-ogoh also built by groups of children around the village. Some artist also usually build one. After being paraded on a convoy around the town, finally it is burnt to ashes in a cemetery as a symbol of self-purification.
text via wikipedia