The Buddha — “the awakened one” — was Siddhartha Gautama, a north-Indian prince of the 5th century BC who abandoned palace luxury to discover why life involves suffering, and taught that suffering ends when craving ends: the Four Noble Truths and the Eightfold Path that became Buddhism, now followed by some 500 million people.
His doctrine fits in a sentence: life involves suffering; suffering comes from craving; craving can cease; there is a path — the Four Noble Truths and the Eightfold Path. From a single wandering teacher it spread from India across Asia and, in modern times, around the globe.
