These are blindspots. You don't even know that such topics exist and hence you can't have knowledge or experience in them. The only way to know about these is to start reading more things written by other people, discuss random topics with them.
Also read
Referenced in:
- Known-Knowns
- Mentoring-Starter-Kit
- Known-versus-Unknown
- Unknown-Knowns
- knowledge-matrix
- knowledge-expands-but-so-does-ignorance
- Known-Unknowns
- knowledge-gaps