拍拍 is the reduplicated form of 拍 (pāi, to pat/clap/beat). Reduplication of a verb in Chinese indicates a brief, casual, or 'try doing' action — like doing it a little or once. So 拍拍 means 'to give a light pat' or 'to clap a couple of times', often used for comforting (pat on the back), attracting attention (clap hands), or lightly removing dust.