1. Tenor trombone: This is the most common type of trombone, and it is the one that is most often used in orchestras and concert bands. It is pitched in B-flat, and it has a slide that extends the length of the instrument to change the pitch.
2. Bass trombone: This trombone is similar to the tenor trombone, but it is larger and has a lower pitch. It is pitched in F, and it is often used in jazz bands and marching bands.
3. Alto trombone: This trombone is smaller than the tenor trombone, and it has a higher pitch. It is pitched in E-flat, and it is sometimes used in orchestras and concert bands.
4. Valve trombone: This trombone has valves instead of a slide, which makes it easier to play certain notes. It is pitched in B-flat, and it is sometimes used in jazz bands and marching bands.
In addition to these four main types of trombones, there are also a number of other less common types, such as the contrabass trombone, the sopranino trombone, and the slide trombone.