Feathers are sometimes confused with down. Feather refers to the external horny structure that forms the body covering of birds. It consists of a quill point, quill shaft and vanes, with or without an after shaft. Duck or goose feathers are hard and heavy and are used for flying and swimming. Down refers to the undercoating of waterfowl. It consists of light and fluffy filaments growing from a quill point. It is soft and three dimensional and can hold air at high altitude and low temperature with minimum weight.

Feathers are also used as filling. They are chopped up and used as a cheaper alternative. But a goose down pillow is much more desirable than a feather filled pillow. Each ounce of high quality down has about 2 million fluffy filaments that interlock and overlap to form a protective layer of still air. It keeps warmth in and cold out. The little pockets of air actually do the insulating. You can flatten down out and it will get back its fluff with a good shake.