Okay, fine, who’s this really for?
Anyone, I suppose, but in reality? If you’re stuck on a remote system that only allows terminal logins, this is a super handy tool to use. If you’re used to text-based editors, like Emacs, Nano, or even vi or vim, you’ll feel right at home in here. You can type in commands and then run queries. There’s even multi-line support for more complex stuff. There’s another side to this too: if you’re the kind of DBA that gets really mad if someone installs management studio on a server, then this might be a solution: it’s got a very small installation footprint, and you don’t get a full UI experience so unless you know all the big T-SQL commands for heavy administration (like for, say, dealing with an availability group or adding permissions, or taking or restoring backups), you won’t get much use out of it. But in a pinch, on a server, in a crisis where you can’t tell if SQL is up and serving queries? It just might work out well for you.
Read the whole thing for an enlightening Q&A session, although the question-asker is kind of a jerk to the answerer.