His teaching is based on his insight into dukha (typically translated as "suffering") and the end of dukkha the state called nibbna or nirvana. Buddha means awakened ones, someone who has awakened from the sleep of ignorance and see things as they really are. He was the founder of buddhism. He was an ordinary person named siddhartha gautama whose profound insights inspired the world.
It is said that when buddha dies, he/she is not reborn but passes into the peace of nirvana, which is not a heaven but a transformed state of existence.