A Song Dynasty statue of the boddhisatva Guanyin
What is a boddhisatva?
A boddhisatva, in Buddhist religion, was a holy man or woman. They were special, closer to God than other people. They were like holy men in ancient West Asia, or saints in Christianity.
Buddhists who were enlightened
Among Buddhists, the main goal of life was to become enlightened. Once you were enlightened, you could stop being reincarnated when you died. Instead, you could enter nirvana (like Heaven) and be one with God. Boddhisatvas were people who had achieved enlightenment, and could enter nirvana. But they chose to stay on Earth anyway so they could help other people towards enlightenment.
Famous examples
In his previous incarnations, before he was the Buddha, the Buddha was a boddhisatva. A lot of Jataka Tales are stories about the good deeds the Buddha did when he was a boddhisatva. But there are lots of other famous boddhisatvas. Many of them are from China, where Buddhism spread in the 400s AD. Some famous Chinese boddhisatvas are Guanyin and Jizo.
Learn by doing: visit a Buddhist temple
More about Guanyin
More about Nirvana
And more about Buddhism
Bibliography and further reading about ancient Buddhism:
At Wat Dhammaram, Chicago, we have a sermon every Sunday at 1 pm on the Vessantara Jataka during the Vessa (Buddhist Lent = three months) in Thai language. On this coming Sunday, October 6, 2019, I was assigned to present the story in Chapter 11: Cho-khattiya or Six Royal Members. We have the original text in Pali. But it is hard to find the English version.
The contents of this story are the most impressive in terms of humanism and spiritual dimensions. …
I think this is what you are looking for? https://static.sirimangalo.org/pdf/vessantara.pdf (Search for “Six Princes”)