Question about B7K ultra

In one day I will have my first Darkglass pedal and to be true I have never use so much pedal so I still a noob. This week I have two concert with my band, and reading about the b7k ultra, I have a question.

I have read a lot of integrade cab sim on the bass, can sound stupid, but what is a cab sim for?

And the more important question, I would like to play directly without speaker, that is why I bought this pedal, could be possible to play directly just with my band and the pedal, or I will need to download first a cab sim for it?

I hope you can solve me this problem, because I doesn’t have enough time to try it before the concert…