Sid was the son of the king in Nepal. A fortuneteller came and said that Sid could either become a mighty king or a religious leader. Sid's father wanted him to become a king so he had specific things done.
Sid's father wanted Sid to choose the king route, so he had gurads follow Sid outside their castle. The guards made sure that Sid didn't see anything or anyone unpleasent or suffering. Sid did not see anyone sick, poor, or sad. Sid didn't see or feel empathy towards other people for a long time.
Sid decided to sneak out without any guards and saw an old man stuggling. He snuck out again for a second time and saw the old man struggling with a disease. His third time outside he saw the old man's family crying because of the old man's death. The fourth time he saw a poor man meditating, looking content.
Sid ran away to seacrh for answers and see how it is in a poor person's shoes. He lived off of food given from strangers, he lived under the shelter of trees and caves, and he joined the ascetics. He was in self-denial because he was an ascetic. He refused and denied everything, but was not able to acomplish. He was abandoned by the ascetics, but still continued his search.
He continued to search and found a tree. This tree is now the Bodhi Tree or the Tree of Knowledge. He meditated under the tree for 49 days and saw his past lives. Since he was aware of the cycle of life, he was freed. He became the Buddha.
The Buddha had freed himself so he stayed in liberation then came back. He wanted to teach others how to escape and he did this for 45 years. His purpose was to awaken the world to the true nature of life. He wanted people to see the understanding of the cycle of suffering and rebirth. He continued, attracted many followers, and tought some of his followers to become teachers. He then died at the age of 80.