A G-string (alternatively gee-string or gee string) is a type of thong underwear or swimsuit, a narrow piece of cloth, leather, or plastic, that covers or holds the genitals, passes between the buttocks, and is attached to a band around the hips, worn as swimwear or underwear mostly by women, but also by men. The two terms G-string and thong are often used interchangeably; however, they can refer to different pieces of clothing. It is usually worn on beaches, especially in South America and tropical countries.
Read more about G-string: Etymology