Okay kiddo, so you know how sometimes people say things that aren't true, but they say them anyway? Well, that's called lying. A "true lie" is when someone tells a lie, but they believe it's true. It's kind of like if you told your teacher that you lost your homework, but you actually forgot to do it. You're telling a lie, but in your head, you believe it's true because you forgot to do the homework. Sometimes people don't even know that they're telling a true lie, so we always have to be careful and try to figure out what's really true.