Okay kiddo, so a nationalist government is a type of government that believes in putting their country first before anything else. In this case, we're talking about the Republic of China, which is also called Taiwan.
The nationalist government in Taiwan used to be in charge of all of China a really long time ago, but they lost a big war to another group called the Communists. So they had to move to Taiwan and set up their government there.
The leader of the nationalist government was a man named Chiang Kai-shek, and he really wanted to make Taiwan a strong and powerful country. He believed in things like protecting the traditional culture of China and having a strong military to defend the country.
The nationalist government in Taiwan was in power for a long time, but eventually, they had to share power with other political parties. They still believe in putting Taiwan first, but now they work with other people to make decisions for the country.
Does that make sense, kiddo?