Siddhartha Gautama founded Buddhism in India in the 6th century BC after becoming enlightened under a bodhi tree. He taught that life involves suffering, but the Four Noble Truths and following the Eightfold Path can end suffering and reach Nirvana. Buddhism spread across Asia over centuries and developed into three main traditions: Theravada focuses on monks achieving Nirvana, Mahayana believes anyone can reach Nirvana, and Vajrayana includes Tibetan practices and lamas.