"Saddles, stirrups, bridles, halters, reins, bits, harnesses, martingales, and breastplates are all forms of horse tack. Equipping a horse is often referred to as tacking up."
That's a good start.
Also polo wraps, pads, and boots (worn on legs not feet) are tack.
Leadropes are not tack.. as the horse doesn't wear it. But they usually come with halters, which is tack.
"Strength is the ability to use a muscle without tension"