This is useful to me and not necessarily for outside consumption.

Vocabulary

The file or document is a spreadsheet. It is uniquely identified by a fileId (Drive API speak) or a spreadsheetId (Sheets API speak).

A spreadsheet contains one or more sheets. In normal life, people also say “worksheet” or “tab”. But not us. We say “sheet”.

To connect back to Excel, a workbook = a spreadsheet = (xlsx) a SpreadsheetML package. It contains at least one sheet.