HP 840791-251 is a Russian-layout laptop keyboard for replacing a damaged or worn keyboard. Its Russian key layout makes it suited to typing in Russian, and the part number identifies this specific regional version.
The keyboard is described as an advanced keyboard with TouchPad for HP notebook models with a 14-inch display. It is listed as compatible with the HP ProBook 645 G2, so it serves as a keyboard and touchpad replacement for that model.
The unit is black and made from ABS synthetic material. It has no numeric keypad, keeping the layout without a separate number pad.