G-string is a type of thong, a narrow piece of fabric, leather, or satin that covers or holds the genitals, passes between the buttocks, and is attached to a waistband around the hips. A G-string can be worn both by men and by women.
Thong is a garment generally used as either underwear or as a swimsuit in some countries. It may also be worn for traditional ceremonies or competitions. Viewed from the front, the thong typically resembles a bikini bottom, but at the back the material is reduced to a minimum.