They are things that you know, that you don't know you know. For example, uncovering links between existing knowledge that uncovers something that then feels obvious.
This happens occasionally where two previously thought seperate fields of study discover a common link with each being able to explain the questions the other had struggled with.
Yup. My daughter (15y) had the perfect example this morning. She said she was thinking about shooting a person with a cannon upwards, then realizing they feel effectively zero gravity at top, and maybe this could be usefull. Then she remembered parabolic flight paths to train astronauts, realized it’s the same thing, and that she started wondering about a thing she already knew.
Lots of people know things deeply in their subconscious that they are fully ignorant of in their conscious thinking. These can manifest as gut feelings, or anxieties, and with therapy, can be identified. Things like "you should leave him", or whatever.
This happens occasionally where two previously thought seperate fields of study discover a common link with each being able to explain the questions the other had struggled with.