The first answer is very good and direct. I might just add a bit of thought to it....

Throughness - this comes from a horse that is very light, supple, and is truly utilizing its whole body effectively - driving from the hindquarters, the horse is not forcing or 'falling' into the bit (becoming heavy in your hands), or stiff like a board. Instead, he/she is like a wel oiled machine - power sits underneath you, but it is totally undercontrol, and can yield (give to you) any part of it's body effectively accomplishing whatever movement you ask of it.

I truly believe that 'throughness' is not just a physical act, but a mental and emotional act for the horse - and for the rider. It is one of the most magical things to achieve with your equine partner.

God Bless,

Misty

Throughness is where the horse directs it's energy flow by pushing from the hind quarters, over the back and down into the bit.