Prior to interviewing with Uber, it is important to understand that the organization promotes new ideas and takes risks, and they promote this among their staff. In asking this question, your interviewer would like to know that you can take initiative in the workplace and come up with creative ideas that promote positive change. Perhaps a new company policy was coming into place, and you helped to execute some changes. Maybe a new employee benefits program was introduced, or new software was implemented. In your example, be specific about what you did and the impact your actions had - whether short or long term.