horses that are suitable for beginners are generally calm, gentle and VERY forgiving of mistakes. A horse can actually be too trained for a beginner! some horses are so well trained that they respond to very,very subtle cues that only an experienced rider would know how to give, a beginner would confuse the horse by accidentally giving these signals in thier inexperience. For example- some horses back up if you pull back on the reins in a certain way, a beginner who pulls on the reins ussually just wants the horse to stop! Or some horses will change gaits or do certains movements solely by a change in leg position or a shift in the riders wieght. A beginner would become very confused by this, as beginners are still learning how to do basic tasks, like stay on the horse, post or steer! A beginner needs a horse that is hardened to these things, and will help teach you basic riding skills. an overly trained horse in the hands of a beginner can be VERY dangerous, as a beginner would not know how to control such a horse, even though with an experienced rider the horse would be almost perfect. Also, some horses have temperments that are unsuited to most beginners. Most beginners can be somewhat timid in thier riding, a horse can sense this, and some horses will take advantage, but if an experienced rider hops on, the horse knows right away to behave. Or, sometimes experienced riders like a horse that is more "forward", that has a certain spirit to it, that doesn't mean the horse is ill trained, but it may have too much energy for a beginner to control well. Other horses may be ok with beginners sometimes, but they crave a challenge. A bored horse will cause a beginner problems, and really wouldn't be happy in a beginners home, because it wants somthing more to do. Does that answer your question a little? There are alot more scenarios, but those are the basics. Think of it this way- noone would say that a winning race horse or olympic level dressage horse was not well trained, or behaved poorly, but it would be an entirely unsuitable mount for most horsemen! Hope that helps. -Neb