This question requests you to define a goal or a set of goals for Facebook Marketplace, which serves as Facebook's platform for selling second-hand items. This suggests that the interviewer is interested in your ability to strategically plan for a versatile platform like Facebook Marketplace, as well as your understanding of the current market landscape and the platform's user demographics. When establishing these goals, you should identify the target user groups of Facebook Marketplace, assess Facebook's strengths and weaknesses, explore potential growth opportunities, and recognize any external threats. Moreover, these goals should be in line with Facebook's overall business objectives.