A slingback is a type of woman's footwear characterized by a strap that crosses behind the heel or ankle. A slingback strap is distinguishable from an ankle-strap in that the latter is a strap that completely encircles the ankle.
Slingbacks can be considered a type of sandal and come in a wide variety of styles from casual to dressy, with heel height ranging from none to high, heel types ranging from as thin as a stiletto to as thick as wedges and they may be either closed or open-toe.
Slingback's straps is usually adjustable through a buckle or an elastic allowing the wearer to slip their foot into the sandal easily without the need to make further (or any) manual adjustment to the strap or buckle, while still holding the foot in the sandal relatively securely. The buckle can be made of metal, plastic, or even sometimes stone.
Wikimedia Commons has media related to Slingbacks.