Document and Trim Size
Document, Canvas, Artboard and Page Size
These terms all refer to how you setup your print project on the computer. It determines where your document will trim during production and where your trim lines will show on screen. (Trim lines are black guide lines)
Trim Size and Folded Size
These refer to what size the actual printed product will be. This is after the print has been trimmed and/or folded. It depends on the right document size and bleed settings.