Pigtails is a hairstyle that is typical for girls and creates a very cute, 'girlish' appearance.
It is therefore a popular hairstyle in girl spanking art. It is also very common in ageplay to make an adult woman look and feel more like a "little girl".
The hair is parted down the middle and tied into two bundles, one on each side of the head, usually above and behind the ear. The bundles of hair are tied with scrunchies, hair clips, or ribbons.
 See also