Resource/Explanation of board reference acronyms, pins, etc.

Well, I'm not sure about higher level, but:

• If you search at http://www.espruino.com/Search you'll usually get pages on each particular peripheral.... and I've just made clicking the pin functions in the reference page link through automatically.
  
• Not sure if you found it, but there's a second board reference at http://www.espruino.com/EspruinoBoard
  
• The pins are usually connected straight through to the chip, so you can check the datasheet on it which gives you an overview of what the actual hardware can do without being too low level.
  
• If you're super interested then there's the reference manual which gives diagrams and exactly how things work and are set up - it's hard work though!