Siddhārtha Gautama (Sanskrit; Pali: Siddhattha Gotama) was a spiritual teacher from ancient India and the founder of Buddhism. He is generally recognized by Buddhists as the Supreme Buddha (Sammāsambuddha) of our age. The time of his birth and death are uncertain: most early 20th-century historians date his lifetime from c. 563 BCE to 483 BCE;
Gautama, also known as Śākyamuni or Shakyamuni (“sage of the Shakyas”), is the key figure in Buddhism, and accounts of his life, discourses, and monastic rules were said to have been summarized after his death and memorized by the sangha. Passed down by oral tradition, the Tripitaka, the collection of teachings attributed to Gautama by the Theravada, was committed to writing about 400 years later.
On leaving the palace in his late twenties, Siddartha began a search for the Truth.
The Great Enlightenment
After asceticism and concentrating on meditation and Anapana-sati (awareness of breathing in and out), Siddhartha is said to have discovered what Buddhists call the Middle Way—a path of moderation away from the extremes of self-indulgence and self-mortification. He accepted a little milk and rice pudding from a village girl named Sujata, who wrongly believed him to be the spirit that had granted her a wish, such was his emaciated appearance. Then, sitting under a pipal tree, now known as the Bodhi tree in Bodh Gaya, he vowed never to arise until he had found the Truth. Kaundinya and the other four companions, believing that he had abandoned his search and become undisciplined, left.
After 49 days meditating, at the age of 35, he attained Enlightenment; according to some traditions, this occurred approximately in the fifth lunar month, and according to others in the twelfth. Gautama, from then on, was known as the Buddha or “Awakened One.” Buddha is also sometimes translated as “The Enlightened One.” Often, he is referred to in Buddhism as Shakyamuni Buddha or “The Awakened One of the Shakya Clan.”
At this point, he realized complete awakening and insight into the nature and cause of human suffering which was ignorance, along with steps necessary to eliminate it. These truths were then categorized into the Four Noble Truths; the state of supreme liberation—possible for any being—was called Nirvana. He then came to possess the Nine Characteristics, which are said to belong to every Buddha.
The Buddha’s final words were, “All composite things pass away. Strive for your own liberation with diligence.”
Source: Gautama Buddha on Wikipedia