Product discovery is the work a team does to learn which problem is worth solving and what might help. It is like asking questions and looking at clues before choosing a route.
A team might talk with people who would use an app, study where they get stuck, and try a rough idea before building the full feature. This can help avoid spending time on something people do not need.
Discovery does not guarantee that an idea will succeed. It gives the team better information to make its next decision.