I once read some useful advice to think of documentation in four categories: For work: 1. Playbook (how to do this thing) 2. Reference (what or where is this

I once read some useful advice to think of documentation in four categories: For work: 1. Playbook (how to do this thing) 2. Reference (what or where is this thing) For learning: 3. Tutorial (practical familiarity) 4. Explanation (deep understanding) I agree that a lot of projects would benefit from more effort in category 4. It might be the most difficult of all to write, though.