Down feathers are the soft, fluffy feathers found beneath the tougher outer feathers of birds, particularly in species like ducks and geese. These feathers provide excellent insulation, helping to keep birds warm in cold environments. Down is lightweight and traps air, creating a barrier against the cold. Due to their insulating properties, down feathers are commonly used in products like comforters, jackets, and sleeping bags. They are highly valued for their warmth-to-weight ratio, making them a popular choice for outdoor gear. However, ethical sourcing is important, as some down is collected in ways that can harm birds.