Often the terms window covering and window treatment are used synonymously. However, it is important to understand the slight differences.
"Window Covering" defines any device used to increase light control or privacy within a window opening. Generally, this transforms the window from transparent to translucent or better.
"Window Treatment" is the broad term describing anything added to the basic window for function or style. The term "window treatment" includes window coverings. Examples of window treatments that are not window coverings include valances, cafe' curtains, and nonfunctional drapes or swags.
In selecting window decor, window coverings are often combined with window treatments that provide style. For example, cafe shutters are may be use with a fabric valance that complements colors of the room.
Interior shutters can be described as both a window treatment and window covering.