What makes ducks different from other waterfowl

Ducks are smaller than swans and geese.
They have squat bodies, and are found in
both freshwater and saltwater. They have big,
flat bills that help them to scoop food off the
water’s surface or from just below it. Small,
freshwater ducks are called teals. Another
group of ducks, called wigeons, have lovely
blue-grey bills. Dabblers are ducks that stand
and fish in shallow water. The eider is a large
sea duck prized for its soft feathers. Most of
the common domestic ducks are mallards.

The fact that they're called Ducks, whereas others could be Geese or Swans.
Also, they quack.

farted