You nailed it with "What is an interface?". Interviewers really mean Java interface. Back in the day, I was told in an interview: "While they were a Java shop

You nailed it with "What is an interface?". Interviewers really mean Java interface. Back in the day, I was told in an interview: "While they were a Java shop, this interview is about general programming concepts." The first question they asked was "What is an interface?".