I love that "unanswered questions in physics" is a category that contains both questions that are really easy to state to a layperson (including ones that seem very simple and easy and are very much not) and questions that require a background in physics to even know what they're asking
"unanswered questions in mathematics" is like this too
and "unanswered questions in biology" has a few easy-for-laypeople-to-understand questions like "why do most animals need sleep" but is mostly full of questions you need a background in biology to understand