Women's panties have their origins in the 1920's when bloomers (long underwear) became shorter and looser as the flapper look came into fashion. The panties of this time were called step-ins. A thong is a panty with a narrow strip of fabric in the back that begins as a "v" shape at the waistband and then tapers to a thin strip by the time it reaches the crotch. This style panty is great if you want no visible panty lines and a smooth appearance.