It's carbonless paper - writing on the top sheet replicates the writing on the sheet(s) below, assuming that you have the sheets in the correct order with the correct facing.I've deducted a star because it's slightly confusing which side of the sheets are which - only one side of the sheet will replicate the writing. The ream seems to be designed to be opened and placed directly into a printer which prints on the reverse face, because the sheets are in that order in the ream. So if your printer prints on the obverse face, then you'll need to flip the ream upside down. I think it would be helpful if the packaging explained this.