Siddhartha was born a prince in Nepal, his father (the King) went to a fortune teller to find out what he might be. The fortune teller said that he might be a mighty King or a Religious Leader.
The King never let the Prince see sadness, suffering, or beggars so he would never fell bad for them and become a religious leader to try and change it. The guards went in front of the prince when ever he went out to get these people off the streets.
One day the prince went outside without his guards making the sad, suffering, begging people get off the streets, so he saw what life was all about. Then the prince did exactly what the King didn't want him to do, feel bad and try to change it.
I am teaching you how to reach enlightment!
Sidd then goes out searching for the truth about life. He left his possessions behind except for his begging bowl where people put things for the prince in. He had to sleep under a tree or in a cave at night, then he joined a band of religious ascetics.
The prince lost so much weight and energy that he fainted, when he awoke he drank a milk bowl and a bowl of rice, the ascetics abandon him for this. He felt so bad that he went underneath a fig tree and started to meditate. He meditated without food or water for 49 days in that same spot nonstop.
The prince achieved enlightenment and freed himself from the cycle of rebirth. He had become the Buddha. He chose to go back into the world and teach others what he had learned over the time that he was gone. For the next 45 years, the Buddha traveled across India preaching fro a message of truth and hope. He then died at age 80.