Descriptions of Fields and Reference Types

I have looked all through the User Guide, and nowhere can I find details of what information exactly each of the fields refers to - only the standard author, date etc are covered. It might be my imperfect knowledge of referencing - but it would be really useful to know the difference between document number and report number, for example, and what is the Type field? I also don’t know what referencing type to use for newsletters and working papers, for example. Are there any descriptions or guidance on fields and reference types out there?

Thanks very much