What am I going to be doing?

Tell me about your ideal work environment.

There are a few points in the interview where the interviewer is going to probe to make sure you understand the duties of the job and the work environment. This is one of them. So it measures your research skills, but it also measures your fit. For example, if you respond that you have enjoyed working with children and that you like the daily interaction with clients and you like to have close relationships with your colleagues, if you are about to be consigned to a lonely outpost with limited interaction beyond phone or chat, you are not going to be a good fit for the position.

It is, however, a BDI question, so they are looking for an actual work environment that you have experienced that you felt brought out the best in you. Try to find a work environment that seems closest to the one you are currently interviewing for, with a similar managerial structure. I hope to Hades that this does match with what you are looking for...I'm not going to ask, if this position doesn't match with your ideal, why are you interviewing for it? I'm guessing you need grocery money.

If school was your ideal work environment, think about it: what made it so good? Structure, intellectual challenge, clear deadlines, interaction with knowledgeable supervisors and working with peers. You can also suggest that the ability to assume responsibility for tasks and complete them on time was also exciting and vital to your daily happiness. (There is one problem with using school as your ideal work environment: it's over. Don't look like you will run back to academia with open arms. So be careful how you phrase this.)

This question can also be used as a measure of your ability to mesh with management. If you have seen their org chart or if this is part of a series of questions that asks about management style or structure, you can reiterate some of the points about management style in this answer. But, be brief: you have already had a shot at those questions.