[atoav]

I interviewed people and I would prefer a broad answer to a broad question. A broad question is an invitation for you to present me a selected platter of knowledge you have aquired about the various forms of interfaces. And the candidate who does that will always outperform a candidate who can't think about those concepts on a broad abstract level and needs to be lead to the waterhole.

"What is an interface?", is a totally legit question that can be answered without thinking about any specific interface. E.g. it could could be described as a systemic boundary between two domains, that is ideally well defined. You could talk about different interfaces, what the advantages and pitfalls of introducing interfaces are, conventions that exist etc.