Each development dimension needs it's own documentation, as each has it's own particular needs.
Documentation for the team that implements the software.
Documentation for the person who uses the software.
An action is a menu item or button press. When activated, and action navigates or executes. The results may be dependent on the context, or by other fields.
A field is a value that the user configures. Fields may have validation.
Documentation for the person who installs, customizes, manages, and administers the software.
Documentation for the person who determines if the software an appropriate solution for the given needs.
Documentation for the company that acquires the software. This relates to the sale of the software source code itself, not the licensing of the of the application.