Button Down Collar
A button-down collar is a type of informal collar found on dress shirts. The difference between a button-down collar and a traditional collar is that a button-down collar has buttons under the collar points allowing them to be fastened to the shirt; whereas a traditional collar is typically held in place with starch or a stiff backing material. Because of this button-down collars appear softer and more loose than traditional collars.
Button-down collar shirts are considered less formal than their traditional counterparts and can be worn with or without ties. Regardless of whether the shirt is dressed up or down with a tie it is still considered a less formal option and thus not worn on formal occasions or with formal articles of clothing like double breasted suits. Single breasted suits are, however, considered acceptable.
The decision on whether or not to actually utilize the buttons on the collar depends on the style that the wearer is trying to achieve. Unbuttoning the collar is considered highly informal and presents a carefree look. Buttoning the collar presents a less casual look however is still slightly informal.
Button-down collars originated as part of the uniform of polo players. Due to the speed at which polo players must ride horses and the bumpiness riders experience while on horseback there is a tendency for things that are not securely fastened to become unwieldy. After a while crafty polo players began adding buttons to their shirt collars in order to prevent the collars from flying up and impairing their vision or distracting them from the game, and thus the button-down collar was born.