One of the people that popularized the concept is Dan Olsen.
Olsen provides many examples of points in problem space: Taking notes in zero gravity, securely and quickly unlocking your phone, or filing your taxes to cite a few. We could add anything else that can be formulated as a need: Preventing a meltdown in a nuclear powerplant, finding the closest fast-food restaurant, or predicting next year’s fashion trend.
Any point in solution space corresponds to something you can build. A concrete product implementation. As engineering teams, we spend a lot of time finding points in solution space meaning designing, architecting, and engineering software products.