Before building a product - how do you know what product to build? While building a product - how do you know what features are the most valuable? After you've built a product - how do you know if to tune stuff or add a new one?
Oh, project managers, how often are we mixed up? We even share the shortcut - PM. When a few years ago many project managers jumped on the Agile bandwagon to become coaches, scrum masters and delivery managers - I thought it will help to solve the confusion. No luck, people still often use project and product manager terms interchangeably.