What did you hear about us?

What they are really asking

Two things are hiding in this one. First, did you do any research, or did you apply to forty jobs without reading about any of them? Second, what does the outside world say about the company? Interviewers are curious about their own reputation, and your answer tells them how they look from the street.

The weak answer is the company's own website read back to them. They wrote it, so they already know it. A stronger answer mentions where you heard about them, one or two specific things, and why those things made you want to apply.

A shape that works

Source, two details, your reason. Say how you first came across them: a friend, a news story, a product you use, a talk at a conference. Name two specific things you've learned, and keep them concrete. Then connect one of them to you. If you've heard something mixed, you don't have to bring it up here; save your honesty for when they ask directly.