Nataraja is the primal diety of Dance. In this form Shiva is shown as the primal deity around whom the entire cosmos revolves. He is the creator, sustainer and destroyer of the creation. His tandava symbolizes the destruction of evil, ignorance and the idea of self. The gestures of the dance represent Shiva's five activities, creation (symbolized by the drum), protection (by the "fear not" hand gesture), destruction (by the fire), embodiment (by the foot planted on the ground), and release (by the foot held aloft).
The word Nataraja means "Lord of the Dance," and this cosmic dance represents the fields of energy moving throughout time. It is believed that as long as Shiva keeps dancing, our universe will continue to exist. But when Shiva finally tires and falls asleep, this universe will run out of energy and the cosmos will pass out of existence.