The best home for a horse is a safely fenced paddock with good grass, free of any noxious weeds that can be harmful to horses. The paddock should also be free of sharp jagged objects, bits of tin or wire, or anything that a horse could injure himself on.
There should be plenty of clean fresh water available at all times.
Horses needs change with the seasons. In the winter he may need a rug, which should be checked daily. In late summer and early winter there is usually less grass around, so he may also need extra feeding. In spring there may be too much grass. A horse that is too fat is just as bad as a horse that is too thin. Overfat horses can be prone to a condition called laminitis, or founder. This is a very painful condition which if left can be fatal. The best way to stop this from happening is to monitor the horse's weight. The horse may need to be locked up for part of each day and night to keep his weight properly managed.
The paddock should be well drained and if it gets too muddy in wet weather the horse should be moved. Horses that are continuously standing in mud can develop infections in their hooves. These can be quite painful and will make the horse lame and unhappy.
There should be shelter for the horse to get out of the wind or hot sun. A man made shelter is ideal but large shady trees can also offer some protection.
Horses are herd animals and will always be happier with a friend for company. Another horse is best but if that's not possible, horses have been known to pal up with sheep or cattle, or even goats.
Horses need regular health care too. Every six to eight weeks an experienced farrier should attend to the horse's feet by trimming or shoeing. If the horse is ridden regularly, especially if on roads and hard ground, then shoeing is usually best.

Once a year the horse should be vaccinated against the diseases tetanus and strangles. Both of these are very contagious and potentially fatal for the horse.
Every two to three months the horse will need to be dosed with a wormer. Wormers come in paste, powder or liquid form. If horses are not wormed, they are likely to develop colic, lose weight, suffer skin conditions or even die. All horses carry worms in their gut. Horse owners must manage the worm population to keep them from causing problems to the horse.
Horses need to see a dentist at least once a year for a mature horse, and every six months for horses younger than four years of age.
If your horse is injured or you think he may be unwell, you should call a vet and have him thoroughly checked over.