The soul of every comforter is what we call the "fill". All decorative pillows and featherbeds are filled with various blends of down, feathers and synthetic fibers.
Down is the light, fluffy undercoating of waterfowl, consisting of clusters or filaments growing from central quill points. Down is lighter than a feather. It is three-dimensional rather than two. Therefore, down has more loft or filling power.
Generally, the colder the climate and the longer the goose is allowed to mature, the larger and warmer the down clusters will be. Different types of down:
White Goose Down: 550 fill power
Hungarian Goose Down: 650 fill power
Polish Goose Down: 750 fill power
Siberian Goose Down: 800 fill power