The shirt was worn under the Justaucorps in the 18th century. A dress shirt, button shirt, button-front, button-front shirt, or button-up shirt is a garment with a collar and a full-length opening at the front, which is fastened using buttons or shirt studs. A button-down or button-down shirt is a dress shirt which has a button-down collar – a collar having the ends fastened to the shirt with buttons.