You can start with this for a big ol list of basics
Then maybe check out some build threads in the DIY Builds category, some of them give great detail and you get to see what people are thinking when they pick certain parts or build things a particular way. It’ll also probably bring up some individual things you want to search, then use the search function to find threads about those. If someone mentions gear drives and you’re wondering what the big deal is go check out some threads on those, if they’re talking about battery amps and you don’t know what that is then search for ESC settings, whatever pops up