Good question. Simply put, it is trimming that would mimic the natural wear a horse would receive in the wild (it's natural environment). The wild horses' hooves are the picture of perfection and what we should all strive for in our own horses. Unfortunately, most of our domestic horses do not get the 10+ miles of movement to wear their own hooves like the wild horses. This is where natural hoofcare comes in.
Due to the poor hoofcare of most of our domestic horses and a lack of a natural lifestyle (stall-keeping), shoeing has become a "necessity". The hooves become too weak to stand up to day to day wear and tear and owners are forced to have their horses shod. All too often this is a "quick fix" and as the hooves deteriorate more and more, standard shoes are replaced by fancy "corrective" shoes. This makes the horse sound for a while longer.
The truth of the matter is that horses were not born with shoes. Shoes are not natural to the horse and in the long run often do more harm than help.
So what should we do for our horses? Easy. Natural hoofcare, natural diet, and a natural lifestyle (24/7 turnout) or as close to it as possible. Not only is this the best thing we can do for their hooves but it is also the best thing we can offer our horses to ensure health and happiness.