Historical negationism

Historical negationism is when people try to deny that certain bad things happened in history, like a war, genocide, or slavery. It's like they're saying these bad things never happened, even when there is evidence (proof) that they did. For example, some people might say that the Holocaust (when the Nazis killed millions of people) never happened, even though there are pictures, documents, and other pieces of evidence to prove it did in fact happen. It's wrong to deny these bad events happened and it's important that we remember and learn from them, so historical negationism isn't a good thing.