Your interviewer will likely ask you knowledge-based questions to understand how well you are able to explain concepts to others. Be prepared for questions like this one by practicing a few possibilities ahead of time. In this case, top-down and bottom-up are different ways to approach information processing and are typically used as design methodologies. You may be asked this question if you are working in product development. Top-down design starts with a higher level system view that is slowly broken down into subsystems. Bottom-up design starts at the subsystem or component level and builds up from there. It's often useful to relate this to a real-world design problem.