If you are currently employed, this question becomes, 'Why do you want to change jobs?' Explain that the job you're interviewing for is just the career move that you're looking for. It's not that you're moving away from a negative, but towards a positive. You're looking to grow your career in the direction this new position can take you.

If you were fired or let go from your previous job, be honest about what happened, but don't offer up any negative details. Most people lose jobs at some point in their careers. You pick yourself up, learn what you can from the experience, and move on.

Don't say: Because my jerk of an ex-boss had it in for me.