Document deliverables are broken down into two categories: Project Control & Product Control.
Project Control involves documenting all of those management activities that control how a project is managed whereas Product Control is documenting everything about the specific product or service.
Each piece of work is accompanied by a deliverable document. if you can think it and perform it, you can document it. Information now becomes 'document centric' as opposed to 'inidividual centric'. In other words the information now is codified knowledge instead of tacit knowledge stored in someone's head.
Dr. W. Edwards Demming, best know for his work in quality control in Japan, advocated the Plan-Do-Check-Act cycle. Without proper documentation, there can be no proper 'Check' and therefore stifle quality control and enhancement.