Siddhartha Gautama was born abound 563 BC. When the child was born, a holy man prophesied that he would either become an emperor or renounce the material world for a great spiritual destiny. His parents gave him the name Siddhartha, which means, "He, whose purpose in life has been attained."
Siddhartha tried to live a life trained to become the emperor, however, his compassion for the suffering of others led him on his spiritual path. His spiritual path led him on the life of extremes. He first led the spoiled, pampered life of the emperor's son, and then left this life for the life of the ascetic. It was these experiences that molded his philosophy of following the "middle way", the life of moderation, rather than extremism.
Most people know the basic story of His life, so I am going to go to the age of 40 when he became the "Buddha". It was near the city of Gaya where he found a tranquil spot under a sacred fig tree, folded his legs, and prepared himself for meditation. It was at this time he took this solemn vow, "Come what may - let my body rot, let my bones be reduced to ashes, I will not get up from here until I have found the way beyond decay and death." Thus determined, full of peace, Siddhartha passed into deep meditation. At the full moon of May in 544 BC. He no longer was Siddhartha, the finite personality. He was the Buddha, "He, who is awake."
The tree under which He sat burst forth into blossom and a fragrant spring breeze showered Him with blossoms. He had achieved nirvana. This is the first state of nirvana, and is liberation from the wheel of rebirth. It is complete soul realization.
The Buddha remained at that spot, as the story is told, for four weeks or more immersing Himself in this experience of illumination. It was during this time that His future teaching was worked out. Buddha's decision to now return to the world and serve is much like that of Moses returning from Mount Sanai, and Jesus leaving the river Jordan after being baptized by John.
When He was greeted by the first initial group of people on His return back to the world, they saw His dazzling radiance and said, "Are you God, or an Angel?" He said, "No, I am awake." which is the literal meaning of the word Buddha.
Thus with His first five disciples, the Buddha began the next forth year stage of His life of teaching the dharma, or path that leads to liberation, and the end of sorrow. It was here that Buddha elucidated his four noble truths.