Two instruments, both tenor, but quite different!
There are two different models of trombones: jazz trombones and symphony trombones (for playing in an orchestra). Some of the parts on these two kinds of instruments vary. Especially noticeable is the size of the bell.
A jazz trombone has a smaller bell, thinner walls, and thinner tubing. The gap in the slide is also narrower. Jazz models are designed this way to make the instrument smaller and increase its mobility. This allows the player to slide quicker as he or she changes quickly from sound to sound.
On the other hand, symphony models are more focused on playing loud, and tend to be larger. A trombone needs to produce sound that is loud enough to reach members of the audience in the back row-all the way from the rear of an orchestra that may have more than 80 members. These thick instruments therefore have a large bell, and can be the first or second loudest instrument in the orchestra.
You could compare the jazz model with a pop or folk singer singing with a microphone, and the symphony model with an opera singer singing without a microphone.