You know how you're not supposed to lie to your friends or family? Well, it's the same with grown-ups too. Sometimes people say things that aren't true, and when they do it on purpose and try to make other people believe them, it's called a false statement of fact.
Let's say you have a blue shirt, and someone comes up to you and says, "Hey, your shirt is red!" even though it's obviously not. That person just made a false statement of fact because they tried to convince you of something that isn't true.
Now, imagine if someone did that about something really important, like how to stay healthy or what's happening in the news. That's why it's really important to always fact-check things and make sure we know the truth before we believe something someone says.