The Black-winged Stilt is a relative of the Avocet, in the family Recurvirostridae. This family of waders includes a few other avocet species from around the world, as well as a few other stilts. The basic difference between avocets and stilts is that the former have fine, up-turned bills and shorter legs, with more pronounced webbing in the feet (making swimming easier); whereas stilts have fine, straight bills and very long legs.
The naming of the stilts, of course, comes from just how long these legs are, looking wildly out of proportion with the rest of the bird. This is particularly apparent when the bird is in flight and the long, red legs trail miles behind!