Art glass is an item that is made, generally as an artwork for decoration but often also for utility,

ART GLASS definition: Art glass is an item that is made, generally as an artwork for decoration but often also for utility, from glass, sometimes combined with other materials. ... Studio glass is another term often used for modern glass made for artistic purposes. WIKI

Finally decided to do this post after reading a post which did not use the term properly, some glass collectors do not know how to apply the term ART GLASS.

Since it can be both decorative and utilitarian, then if Loetz creates a line of perfume bottles with stoppers, it is still in the Art Glass category. Same for decanters, centerpiece bowls, console sets, tooth pick holders, pitchers, celery vases, barber bottles, etc.

In my opinion, utilitarian decorative glass was the 'bread and butter' of any high class glass manufacturer. Especially during the late Victorian early Edwardian eras. Many utilitarian items were in use then, made with glass or ceramic. Note the Loetz pieces in the Palda catalog page under the decanter category. The Bohemian/Czech decorative lamps in other wholesale catalogs.

Small pieces were also created as whimsies for the curio and other cabinets, top of the grand piano, or mantelpiece. Those are all the mysterious glass pieces which are too small to have any type of function other than a pleasing decoration.