Shoulder:  This type is not usually worn as a single layer, but rather combined with other lengths.   It's normally used for semi-formal and formal weddings.

Elbow:  This style is best worn with short or informal gowns.

Waist:  Like above, this style is best worn with short or informal gowns.

Fingertip:  This style is best worn for semi-formal and formal weddings.

Knee:  This style is best worn for semi-formal and formal weddings.

Floor:  This style is worn for semi-formal and formal weddings.  The veil reaches the floor and is often combined with one or two shorter layers.

Chapel length:  This style is worn for semi-formal and formal weddings.  The veil reaches the floor and is often combined with one or two shorter layers.

Cathedral length:  This style should only be worn for formal weddings with gowns that also have cathedral length trains.   One foot or more of the veil should extend onto the floor, past the train of the gown.