This page explains the different types of trombones. There are many different types of trombones that are used in a band.
The Contrabass Trombone
This is the lowest trombone of all trombones. It can reach the same pitched notes as the tuba.
The Bass Trombone
Very similar to the tenor trombone but it has a larger width. This trombone includes a very large bell to get a deep and smooth tone.
The Tenor Trombone
This trombone is the most commonly used and most preferred trombone for all players of this instrument. It produces a smoother and high sound then the bass and contrabass.
The Alto Trombone
This trombone is pitched an octave higher than the tenor. This replaced the tenor when higher notes were needed.
The Soprano Trombone
The soprano trombone is a much smaller instrument then others. It is Pitched an octave higher then other trombones. This instrument is rarely seen in bands.
The Sopranino and Piccolo Trombone
The rarest trombone out of them all. Has the same pitch and volume as the Soprano Trombone but it is a little smaller in size.