A pillow is a type of beddingó a small (and usually soft) 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 which are pillows that are purely decorative and not designed for support or comfort. There are ways to determine if your pillow is still useful or not. If you fold your pillow in half and it doesn't spring back, it's time to get a new pillow.
Pillows contain a filler made from any of a variety of materials including, foam, synthetic fills, feathers, or down. Traditionally straw was a common filler, but this is uncomfortable and rarely used today. Historically feathers and down were the choice of the rich; today artificial fills are the most common.
The fill is then surrounded with a cover or shell made of some form of cloth or silk, commonly referred to as the pillow case. Pillows on furniture normally include a zipper in this cover so that the fill can occasionally be removed and the covering laundered. Bed pillows do not have this feature, and instead a case is used that can be frequently and easily removed and washed.