A Buddha describes a person who has attained full enlightenment and has eliminated all negative qualities and developed all positive qualities. A Buddha is omniscient (knows everything) and can be a guide and helper to other human beings.
The historical Buddha lived about 2,500 years ago in India and was the Prince Siddharth of the Guatama clan. According to tradition he rejected his life of luxury to search for a way to end suffering. He eventually achieved enlightenment and began to teach.