NCR (No Carbon Required) paper is used in multi-leaf business forms to avoid the mess and inconvenience of using carbon paper. A "set" typically consists of a white top sheet plus one or more tinted under-sheets.
Sets can be numbered if required, and can be supplied in "loose" sets, where just the component parts of each set are glued together, or in "pads", where 50 or 100 sets are glued to form a convenient pad. Typical uses are for invoices, credit notes, receipts, business forms, and other situations where one or more copies of a document are required