Why would you interview at a company if you don't know what they do?

Interviewing is a chore, I'm not going to invest my time in doing it unless I think I'll enjoy being there, which requires at least approving of what the company does.

(I would be a little less choosy if I didn't have a current job, but still probably don't want to write software I have strong moral objections too)

Of course I know what they're doing (or the external reflection of thereof). I still ask. I have yet to find a question that will tell me so much using so little.

Interviewed by some startups (Berlin) I have been asked if I know or to explain them what they are doing... and the funniest thing is they were serious.

Most companies should have that explained on their website - If you haven't done enough diligence to repeat what's on the website, you may not be a good candidate.

Oftentimes what the website says, what the sales team is selling, and what the engineering team is doing are three different things

I've probably read it, but I doubt I'll have memorized it enough to regurgitate it back.

And usually it's just BS marketing fluff.

C’mon. You should at least know the industry and major product.

Maybe they want to know if you know their business? Seems like a fair question to ask.

It's a fair question.

The only trouble is that the vast majority of companies can't be understood if you don't already know the business.

Research before the interview. Always know going into the job what the company does, as it'll help you infer where you can add value.

My point being that the vast majority of research will not tell you anything meaningful about the company.

And that’s a valid answer. “I went over your web site and read some press releases but I’m not quite sure what you do yet. I think it is along these lines...can you explain further?”