Your horse needs a shelter just like you. If your horse is outside, then you need to have some type of shelter that your horse can get under when it rains or snows. The shelter should be large enough to accomidate all the horses that are in your pasture so they will have room enough to relax and move without biting or kicking.
If your horse is in a stall, then the stall should be no smaller than a 12 x 12 foot area. The stall that your horse is in should provide adequate feed, water and a place for rest, and exercise. It should be safe and sanitary.
It is also perferable that your stall opens up into a back paddock so that your horse can get sunshine and fresh air. If your horse stays in a stall all day then you need to provide it with daily exercise. This may be riding, round pen work, or just taking them on a walk. But, horses prefer atleast a few hours a day in a open pasture to run, roll, and graze.
Stalls can be bedded with sawdust, shavings, or straw. The bedding in the stall should always be kept clean and dry. If it becomes wet or nasty then this could get into the horses hoof and cause problems there. The stall needs to be cleaned out daily so that damp or dirty bedding won't get stuck in the horses feet and cause illness.