Watching Western Dressage is interesting.
Reading about it is ...... challenging unless you have a Dictionary of Equine Terms memorized.
I'll give a definition a try.
Dressage is teaching a horse a predetermined set of skills. Western Dressage is teaching a horse general skills used in Western events such as a halt, a working trot and turn on the forehand. It is not about teaching a horse English Dressage moves that are used in English events.
Unlike Western Pleasure, the horse is not shown his poll below the withers. The head position should be natural to the breed's conformation.
What kind of horse do I need?
Horses are shown at the walk, the jog, the lope and any special gaits a breed may have.
Patterns can include flying lead changes, halts, circles, serpentines, travers, renvers, half-passes and leg yields.
What kind of tack do I need?
Any Western type headstalls, Western cavessons, hackamores, Native bridles, and bitless bridles.
A standard stock saddle, national, working saddle, Aussie, native or western side saddle is used but silver equipment will not count over a good working outfit. A horn is not required but western style fenders are required.
Saddle blankets are usually natural colors.
The rider must use two hands with a snaffle bit. A rider may use one or two hands with a curb bit. Switching from one hand to two hands or vice versa during a test is considered an error.
What should the rider wear?
Traditional shirts and pants with chaps, shotgun chaps and chinks if wanted, a Western hat or helmet, boots and a belt.
The rider shouldn't wear flashy clothing that takes the judges eye away from the horse. Shirts tend to be solid colors with a bit of trim for women.