This framework was introduced to me during an excellent presentation at the University of Oxford's Said Business School by Iain Lewis of Torpedo Group. His spin was more business & digital marketing focused than the original - which was created by YouTube to show the trickle down effect on their platform.
To extend his point, for a Professional Services business the "hero" content would be the glossy magazines, the budget day seminars & the research pieces.
The "hygiene" would be your brochure website. "Who we are", "what we do" "contact us".
The one that everyone struggles with is the "hub". The on-going blog, the on-going newsletter - the timely, highly relevant & authentic content - which is where you need your best brains contributing.