I want to improve my exposition and writing skills, but whenever I think "what do I know that I can explain to people that isn't explained well elsewhere?" not much comes to mind. I think that happens because it is hard to just do a search of everything that I know. The main topics that I know are math and rationality (mostly LW epistemic rationality, but also a little instrumental and LW moral philosophy). So I ask:

What is a topic in math or rationality that you wish were explained better or explained at a different level (casual, technical, etc.) than what already exists? Like, something that you know now but wish had been explained to you better, something that you don't know but wish you did, or something that you wish you could explain to other people but don't know of any sources to send them to.