There are a LOT of different facets of product design in general, and some I cannot explain very well in person to people.
From the business perspective, there is value-chain management, market planning, feature planning and so on.
The part I usually can’t explain well is the important and role of usability and user-experience design in Product Design.
I finally got a definition worth repeating from Susan Wu.
As product designer, your role is similar to that of a conductor of a large symphony. Only, your instruments are peoplesâ€™ emotion states. Each user experience is the orchestration of numerous emotion states. The value of a customer to you is completely correlated with his/her set of emotional reactions. To add complexity, the timber of each note varies by instrument and by person. For example, the emotional footprint of surprise is different than that of longing. Surprise has a big high and tapers off, leaving it with a short tail. Some people may be frustrated by a feeling of longing, whereas some people may find it stimulating. Ad infinium.
In short, this matters because emotional intensity is the most important filter by which people determine how to spend their time and energy. If you understand what the emotional relationship with your user feels like, you can then figure out what the possible range of monetization opportunities might be.