First, I should explain who Siddhartha Gautama was. He's the founder of Buddhism, right? Born in Lumbini, which is in modern-day Nepal. His life story is important—prince who left his palace, saw suffering, and sought enlightenment. The Four Noble Truths and the Eightfold Path are central teachings. Also, the concept of Nirvana.

Wait, but maybe the user wants more details on the teachings themselves. The Four Noble Truths: existence of suffering, cause of suffering (craving), end of suffering (nirvana), and the path leading to the end. The Eightfold Path includes right view, intention, speech, action, livelihood, effort, mindfulness, and concentration.

Should I mention different branches of Buddhism? Theravada, Mahayana, Vajrayana. Maybe some key terms like karma, samsara, dharma. Also, the difference between Theravada and Mahayana views on Buddha—Theravada sees him as a human who achieved enlightenment, Mahayana has more reverence and celestial Buddhas.