This video talks about two basic ways horses learn: classical conditioning, 'this predicts that' learning, and operant conditioning, 'learning by consequences'.
When a person understands some basics about how horses learn, they will find it easier to get desired results while also minimizing the chances they cause their horse a behavioural injury.
Behavioural injuries can occur when a horse is exposed to training techniques that hurt or scare them, or when a person unknowingly creates a situation where the horse learns to fear certain events or experiences.
These injuries take time and special retraining to overcome, and in some instances can even scar a horse for life.