Almost all brass instruments have movable tuning slides, but the only one that is played by moving a slide is the trombone.
A trombone is a brass instrument played with a slide.
All brass instruments (except the sousaphone) have slides. They are used to adjust the pitch, sharp of flat. The instrument that is played using a slide is the Trombone. It also has a slide on the back that is used to tune, or adjust pitch.
trombone
a trombone is played by blowing air in the thing and moving the slide
That instrument is called a slide whistle. It produces sound by varying the length of the air column inside the whistle by moving the slide up and down.
On piano and other keyed instruments, this is called a glissando.
Unlike the rest of the brass family, trombones change notes by moving a slide instead of using valves.
A tuning slide is a movable part on a musical instrument, typically found on brass instruments like trumpets or trombones. It is used to adjust the length of the instrument, which changes the pitch of the notes produced. By moving the tuning slide in or out, musicians can fine-tune the instrument to play in tune with other instruments or to adjust for temperature or humidity changes.
That would be the trombone. The trombone has a main slide instead of valves to alter the length of tubing that the vibrating air has to travel through to change the pitch of notes. All brass instruments have tuning slides to slightly lengthen or shorten the tubing length to help tune the instrument.
A brass instrument with a slide to make notes
The difference with the trombone is that it is the only instrument with a slide. That slide is what makes it unique.