Spreadsheet documentation may do any of the following:
- Specify the intended working of the spreadsheet
- Record what was done
- Explain how the spreadsheet works
- Instruct the user how to use or update the spreadsheet
Ideally, a spreadsheet would have documentation serving all four purposes.
A specification may be anything from a single sentence to a separate, long, document. In essence, it describes the theory of the spreadsheet rather than the implementation.
A record of what was done does not necessarily contribute much to the understanding of the current state of the spreadsheet, if it describes changes that were made much earlier in its life.
An explanation describes the implementation of the spreadsheet. Instructions are often used to remind users how and when to perform manual processes, such as running a macro, or what inputs are required.
Documentation is usually easier to understand if it is written for a single purpose. It really helps a user if instructions are written (and labelled) as instructions, rather than buried deep in the record of a change.