Wikipedia
The wonsam is a female ceremonial topcoat in hanbok, Korean traditional clothing. It was worn by queens, high-ranking court ladies, and royalty during the Joseon Dynasty of Korea (1392-1910). It is also called 'daeui' (大衣, big clothing), 'daesu' (大袖, wide sleeves) and 'jangsam' (長衫, long clothing). The queen, princess consort, and consort to the first son of the crown prince wore it as a soryebok, a robe for small ceremonies, while wives of high officers and sanggung (court matrons) wore it as daeryebok, a robe for major ceremonies.
The color and decorations of the garment around the chest, shoulders and back represent the wearer's rank. For example, the color yellow was used for the wonsam of empresses, red for queens, jajeok (紫赤 magenta) for concubines and princess consorts, and green for princesses and women of the noble yangban class. Commoners were allowed to wear the green wonsam only for their wedding ceremony.
Varieties of silk were used as the fabric. Wonsam for winter were made with dan , a thick silk with a glossy surface formed with a satin weave, and wonsam for summer were made with sa , a loosely woven silk.
Unlike the po, an indigenous Korean overcoat with narrow sleeves, the wonsam was based on an overcoat with broad sleeves of the Chinese Tang Dynasty. The Chinese clothing system was introduced to Korea when King Munmu, the 30th king of the Silla Kingdom, reformed women’s clothing in 664 AD. As an adaptation from the original model, the wonsam gradually evolved into a distinctive form characteristic of traditional Korean clothing.
Today the wonsam is worn primarily in representations of Joseon royal ceremonies and as a wedding garment, and in a much simplified version when performing traditional Korean dances.