A conventional aircraft wing has an upper skin and a lower skin, and is usually made from metal.  Due to the two skins, a conventional aircraft wing may be too heavy for certain applications and is more difficult to construct than a wing formed from a single skin.  A conventional aircraft wing can be prohibitively expensive and too time consuming to be advantageously used in some applications, such as for example in wind turbines. 
A traditional Rogallo wing is formed from a conical single sail-fabric connected between various supporting ribs.  The Rogallo wing is the type of wing that was used in early hang gliders and is now most commonly seen in kids' kites.  The Rogallo wing is a simpler design than a conventional aircraft wing, but requires more maintenance and has a shorter life-span than a conventional aircraft wing.