The baritone horn and the euphonium are very similar instruments that are played the same way. You'll see both featured on this page. Most young students begin on a baritone horn, and upgrade to a euphonium later. Check with your teacher if you have questions.

Soooooo I bought a greenscreen. pic.twitter.com/Vk3M0GU8Ym

— Abby but FFXIV Soundtrack Hype (@GoofyEuph) June 29, 2019