A pillow is a large cushion support for the head, usually used while sleeping in a bed, or for the body as used on a couch or chair. There are also throw pillows (also called toss pillows), which are pillows that are purely decorative and not designed for support or comfort. Outside the USA these are generally considered and white a type of cushion, with the term pillow reserved for the pillows on a bed.
Decorative Pillows serve a dual purpose. They likely have fancy cover material which serves to decorate the room where they are found.