Have you ever played with a toy trumpet or seen someone playing one? Well, a natural trumpet is like that, but instead of being made of plastic, it is made of metal and it doesn't have any buttons or valves to press.
When you blow into a natural trumpet, the air goes through a long tube inside the trumpet. The tube gets wider and wider until it flares out at the end. The flare makes the sound louder and clearer.
Now, the really interesting thing is that to change the pitch of the natural trumpet, the player has to use their lips to make different buzzing sounds. The tighter the lips are, the higher the note will be.
Natural trumpets were used a lot in music from a long time ago when there weren't any buttons or valves on trumpets yet. People who played the natural trumpet were really skilled because it was harder to make different notes than on modern trumpets.
Today, some people still play the natural trumpet because it has a really unique sound that can't be made by a modern trumpet. It's pretty cool!