white panties
Plain, white colored panties. Sometimes it may also be notably accessorized with a tiny red ribbon on top as mostly seen in anime.
In Japan, white panties is seen as very cute and/or sexy for a woman to wear and, in most cases, white panties is mostly seen as the driving force of ecchi and hentai art. This is in contrast to America where it is considered to be childish and silly for a woman, even a teenager nowadays, to wear them, since they are typically worn by little girls.