A hairstyle with two ponytails, one on each side of the head, is called pigtails.
The style is made by parting the hair, usually down the middle, then gathering each section into a separate bundle secured near the scalp. The hair may be left loose, tied into ponytails, or braided. Because the two sections resemble small tails, the plural term “pigtails” is commonly used.
The word has an older and more varied history. In the 17th century, “pigtail” was used in American English for a twisted bunch of chewing tobacco because it resembled a pig’s tail. Later, the term became associated with braided hairstyles. A single long braid has also historically been called a pigtail or queue, so usage can vary by region and period.
A common mix-up is that pigtails do not have to be braided. Two unbraided side ponytails are widely called pigtails, while “bunches,” “twin tails,” or “twintails” are also used in some English-speaking and Japanese contexts. Two buns on the sides of the head are a different style, often called space buns or double buns.