Korenization is when people try to make things more Korean. Imagine you moved to a new place and you want to fit in. You might start wearing clothes like everyone else there, listening to their music, learning their customs, and speaking their language. That's kind of like korenization.
In the early 1900s, the Korean government wanted to be more independent from other countries, especially Japan. They decided that they wanted to use the Korean language more and make their culture stronger. They wanted people to learn about Korean history, eat Korean food, and use Korean names. So they made it a priority to korenize everything.
One really big way they did this was by changing people's names. Many people in Korea at the time had Chinese names. The government wanted people to have Korean names instead. They also wanted people to use more traditional Korean dress, like hanbok, instead of Western clothing. They even changed the way people wrote Korean by making it more like how it was written long ago.
Overall, korenization was a way to make Korea stronger and more unique. It was important to the people at the time because they wanted to be proud of their country and its culture.