Nearly all of the interviews I've had have been with multiple people. I suppose the purpose is to get several opinions on the candidates. Even more fun is the panel interview where they write down all of your answers as exactly as possible.
Generally, one of those people is the supervisor of the position for which you are interviewing, and I try to ask who that person is in order to make sure they get the proper attention.
Usually, I address the person who asked the question, but also glance at the other people while answering. In some interviews, one person asks all of the questions, and in others they trade off asking questions, which can get confusing.
Try to take it all in stride and not get flustered.
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I'm not autistic, although I do not consider myself neurotypical. I've been diagnosed with major depression and socially avoidant personality. Bonus: bipolar disorder.
~My soul must be iron, because my fear is naked.~