A throwing knife is a special kind of knife that is made for throwing, like how you might throw a ball. But it's only for grown-ups who know how to use it safely!
The knife has a very sharp blade and a heavy handle, which helps it spin through the air when you throw it. It's like a top, when you spin it, it keeps going until it falls over. When you throw the knife, you want it to stick into something. But you have to be very careful not to hurt anyone or break anything when you're throwing it.
It takes a lot of practice and skill to throw a knife properly. Grown-ups who use throwing knives often use them for competitions or for fun, but they always make sure to follow safety rules and use them in a safe place.