A pillow is a cushion designed for the support of the head, and it is typically used for sleeping on a bed.
A pillow can also be used for the body when lying on a couch or chair.
The inside of a pillow consists of filler.
Filler generally is made of foam, synthetic fills, feathers, down or other material.
Historically, straw was a filler, but this was considered uncomfortable and is not used today, at least in Westernized nations.
Feathers and down are often considered the best pillow fill because they offer the advantage of softness and the ability to contour to the shape desired by the user, at least to a greater extent than foam or fiber-based pillows.
Hypoallergenic varieties of down pillows are available that allow people sensitive to down to not be bothered by it.
In the Far East, especially Japan, buckwheat is often found as a filler.
Buckwheat pillows are often smaller than a standard or Western style pillow.
The fill of a pillow is surrounded with a cover constructed from cloth or silk.
This cover is typically referred to as the pillow case or slip.
Some pillows feature a more decorative cover called a sham.
A sham is enclosed on all sides and generally has an opening in the back through which a pillow can be placed.
Mattress pillows that are rectangular in shape generally do not feature zippers, but instead one side of the pillow is left open.
Most pillow manufacturers recommended that pillow covers be washed regularly since they can become dirty and be a haven for dust mites which can cause allergies.
Some pillows themselves can be thoroughly washed, but some, such as memory foam, can only be spot cleaned since a machine wash would effectively destroy the pillow.