Here is a very clear statement about understanding your product:
“Don’t start a business if you can’t explain what pain it solves, for whom, and why your product will eliminate this pain, and how the customer will pay to solve this pain. The other day I went to a presentation of six high tech startups and not one of them had a clear idea for what pain they were proposing to solve.”
— Joel Spolsky, Micro-ISV: From Vision to Reality
I also like the advice from What color is your parachute?, that companies hire a person to solve a problem and they don’t want to get new problems. They buy products exactly the same way.
What problem does your product solve?
What problems does your product create?