Choe Je-u was a person who lived a long, long time ago in Korea. He was born in the 19th century, which was about 100 years ago from where we are now! Choe Je-u was a very important person because he had a big idea of how people should live their lives. This idea was called Donghak, which means "Eastern learning".
Now, Donghak sounds like a very fancy big word, but let me see if I can explain it like you are 5 years old. Donghak is basically an idea that says everyone should be equal and treated fairly. This means that whether you are rich or poor, young or old, boy or girl, you should be treated with respect and kindness.
Choe Je-u wanted everyone to live a happy life where there was no fighting or war. He thought that people could do this by following a few simple rules. These rules included things like respecting your parents, helping others, and being honest.
Choe Je-u also believed that everyone should have the opportunity to learn and read. He thought that if people knew more about the world, they could make it a better place.
Choe Je-u's ideas were very important because they helped people see that life could be better if we treated each other with kindness and respect. Even though Choe Je-u is no longer with us today, his ideas still live on through the people who believe in Donghak.