The project is the scope and purpose of documentation required for a product, be it software, mechanical, electrical, or any combination of the three.
A software program may require a user manual, administrator guide, help pages, training materials, marketing aides, and presentations. A mechanical device may require an installation and operation manual, preventive and corrective maintenance procedures, training materials, an illustrated parts list, technical bulletins, and specification sheets. Electrical documentation may include functional descriptions, hazard analysis reports, user guides, and troubleshooting instructions.
Documentation for a major project like a power plant would include software, mechanical, and electrical elements broken down into systems. Systems may relate to types of equipment (all conveyors), areas (all equipment related to the boiler), or functions (the flue gas system).
The client will specify elements of the project and the documentation necessary. They may have existing templates or documentation specifications, but they may ask the technical writer to provide outlines and formats.