What most people mistake for a pocket, the small flap in the crotch region of women’s underwear is actually an essential element called a “gusset.” No, it’s not for storing spare toilet paper, as some have joked; rather, it’s to encourage genital health and comfort.

In order to prevent skin irritation and bacterial infections, underwear with a gusset—usually constructed from the same fabric as the rest of the garment—is designed with more ventilation.

By acting as a buffer between the skin and the underwear’s internal seams, it lessens the likelihood of irritation and possible health problems.

Contrary to popular belief, not every pair of underwear has a gusset. Designs that are more decorative and less functional, created for temporary use, often leave this component out. This design choice highlights how underwear for women strikes a balance between form and function.

Everyday underwear features a gusset, which emphasizes its significance for genital health and shows how even seemingly insignificant design details can have a big impact on people’s well-being.