He is on his way to town with his tutor's son/friend.
He sees a dead man, a sick man, and an old man.
He is meditating under the tree and sees what is happening in the universe while reaching enlightenment.
Siddhartha was a boy who was kept inside his place/castle his whole life because his father was told something bad would happen to the kingdom if he left it. One day, his tutor brought his son over. They became best friends and played with each other everyday. When they got older Siddhartha wondered what it was like outside. He asked his friend where he was going and his friend said he was leaving to go home. Siddhartha wanted him to stay, so he told him he could provide for him and his father but his friend said he had other family out there as well. So, Siddhartha left with him. On the way to the friends house, Siddhartha saw three things. He asked questions like,"what is that?" and his friend answered with a dead man, a sick man, and an old man. Siddhartha was extremely innocent he didn't know anything. So he left his family and wanted to find the meaning of life. He became a monk. One day, he sat under a tree and began to meditate. Suddenly, he could feel the universe, like it was telling him it's secrets. That was the day he became the ''enlightened one". He also became a Buddha.(teacher) At first he didn't want to teach others,but then Brahma convinced him, and he taught others the meaning of life, dharma, peace, the 4 noble truths, the Eight fold path , the path of balance(The Middle Way),etc. The Buddha's teachings spread all around the world. One way Buddhism spread is by other people teaching others about it. They help people interested in Buddhism and the people interested in Buddhism make other people interested in it. Another way Buddhism spread is by the king not being pleased with the kingdom's harmony so he became a Buddhist and told monks the spread out and build monestaries and teach others about Buddhism.Prince-monk-enlightened/Nirvana-Buddha/teacher