The document discusses how to gather user feedback throughout the product development cycle to build applications based on user behavior and interests. It recommends starting with discovery techniques like surveys and interviews to understand user frustrations. Then use personas, scenarios and prototypes to define requirements. Conduct remote usability testing on prototypes to inform design decisions. Finally, use analytics on the released product to understand how and why users interact with it. The goal is to turn frustrations into desired features and build applications that meet real user needs.