The American bustle or over bustle means the train is gathered up and fastened over the rest of the skirt, resulting in cascading folds. This works best for ball gown wedding dresses or gowns with cathedral-length trains.
The French bustle or under bustle tucks beneath the skirt, creating a tidy billow or two of fabric. It's recommended for A-line, sheath, and mermaid or trumpet gowns.
The royal bustle or Victorian bustle is a more elaborate option, as the train is affixed down the back of the dress at multiple points, creating dramatic folds. Try it out on a very full ball gown or a cathedral-length train.
The ballroom bustle disguises the train altogether by fastening it beneath the skirt at several attachment points. Clearly perfect for a ball gown, this type of bustle can actually be used on most silhouettes.
The bow bustle adds a little extra romance to the gown. It attaches similarly to the over bustle, but is secured with a ribbon or sash. Best for A-line wedding dresses.