The Holodomor was a really bad thing that happened in Ukraine a long time ago. It was like when you're really, really hungry and you can't find any food to eat, but way, way worse. Some mean people who were in charge of the government in Ukraine decided to take all the food away from the people who lived there. They did this on purpose, and they didn't care that lots of people would die because of it.
Many people in Ukraine died because of this, and it was very sad. But some people didn't want to admit that it happened or that it was as bad as it really was. They didn't want people to know that their government did something really, really mean, so they tried to pretend that it never happened.
This is called denial of the Holodomor. It's like when you did something wrong and you don't want to get in trouble, so you try to pretend it didn't happen. But it's not right. We should always tell the truth, even if it's hard or embarrassing. And we should remember what happened during the Holodomor so that we can make sure it never happens again.