Thanks to reviewers from Chris Ridd, Jean-Noël Rouvignac, and Violette Roche. I have added a chapter in the draft OpenDJ Admin Guide called Understanding Directory Services. This is an attempt to provide some context for new directory administrators in about 10 pages.
It is easy to fill pages with high-level content like this. It is harder to gauge whether it will help readers who are new to directory. If you are new to directory and read our introduction, leave a comment here or log an issue for specific problems or suggestions.