On Prince Siddhartha's travels he saw 3 forms of suffering. He saw a sick man, a dead man, and a old frail man. This troubled Prince Siddhartha and he wanted to do something about it.
Prince Siddhartha's royal life was not forfilling, and he wanted to find true happiness. Siddhartha decided to become a Asectic, to find happiness and peace.
On the Princes 35 birthday he bathed in a river and sat under circle of trees. He felt soon he would be enlightened. Prince Siddhartha studied rebirth and the importance of karma, and then was known as Buddha.