For those who are going to own a horse, then they must be ready to accept the responsibility that comes with them. They are a beautiful and valuable animal which requires proper care.
Horsemanship means developing the skills and training of a horse. Added to this is their overall care.
As a live animal, the horse requires proper feeding and housing. Feeding is using comprised of field feeding when the seasons are right, and then the addition of hay and grain to supplement their diet.
When it comes to housing, this is going to depend on the weather conditions. Most horses fare quite well left out to pasture the majority of the time, provided they have some type of shelter to protect them from the elements.
Every horse needs at least some basic training, even if they are not going to be ridden. They need to be halter broken so they can be handled. Most who own horses want to be able to ride them, which means introducing them to the saddle.
From here, training extends to what the purpose of the horse is going to be. Some will be used for sports events such as racing. Others may be used for equestrian events.