Down keeps us warm by trapping air within the thousands of plumuels, like really comfortable insulation. White Goose Down has always been favored. Down from older birds and those raised in cold climates is more robust and keeps it loft longer. Younger birds produce smaller and less robust plumuels. Less expensive and more common Chinese down usually carries a 550 to 575 fill power.
Problems can occur if the down shifts to the comforter's ends and sides.
It looks like a series of window panes stitched through the top and bottom of the shell. It prevents down from shifting. The needle does not pass through the comforter itself. This eliminates cold spots and allows the down to puff to its maximum potential. Follow the care label.