It makes coffee............. It's a Di with a preamp in it. The preamp has tube emulation curtuitry which you can use to get a tube like warmth and/or growly distortion. There's lots of info on this product on TB. Do a quick search.
First,it's a great way to get a good signal to the board in the studio or in a live situation as a direct box.Second it works real well as a preamp and amp modeler.They come with written out settings for different amp sounds like an SVT sound or a Fender Bassman.I had a Carvin R1000 head and was always trying different settings to get a tone I liked.I bought a Sans Amp bass driver,set my amp EQ. flat and set the bass driver to the SVT setting and it sounded great.No more fooling with the amps EQ to get a good sound.Now I use the rackmount version,the RBI,and I love it.