Viewed from the front, the thong typically resembles a bikini bottom, but at the back the material is reduced to a minimum.
Thongs are almost always designed to cover the genitals, pubic hair, anus, and perineum, and leave part or most of the buttocks uncovered.
The back of the garment typically consists of a thin waistband and a thin strip of material, designed to be worn between the buttocks, that connects the middle of the waistband with the bottom front of the garment.
It is also used as a descriptive term in other types of garment, such as a bodysuit, bodystocking, leotard or onepiece swimsuit in the context, "thong backed."
One type of thong is the G-string, the back of which consists only of a (typically elasticized) string.
The two terms G-string and thong are often used interchangeably; however, they can refer to distinct pieces of clothing. Thongs come in a variety of styles depending on the thickness, material, or type of the rear portion of fabric and are available for both men and women throughout most of the world.
Source: Wikipedia, Facebook: Tribo Surfon