In years gone by horses were left to roam the plains, free to do what they liked. Normal horse behaviour in the wild is quite complicated, with different social hierarchical groups and complex herd communication. In the wild horses are responsible for all aspects of their survival, domesticated horses on the other hand rely on us for all aspects of their care, such as providing food, body care/grooming, and making sure they are warm in winter and cool in summer.
The majority of horses adapt very well to domestication, but they are expected to live in small stables and graze in small, enclosed areas, and this environmental change, compared to their feral counterparts, gives rise to a range of abnormal behaviours that can be distressing for both horse and owner. Vices, such as box walking, crib-biting and weaving are commonplace and are usually caused by poor management, so it is essential you know how to avoid these. It is important that we ensure our horses are kept in the most comfortable conditions possible to ensure their health and sanity!
As a horse owner you also need to know how to handle your horse correctly to avoid potential problems, both ridden and on the ground. Issues than can crop up include problems with clipping or shoeing. These can be avoided if you know how to deal with them, and prevent them from happening.