Horses are domestic animals, they are very strong and have been used as beasts of burden for thousands of years. Horses carry riders, they also pull chariots, carts plows and the like. You knew that didn't you?
Wild horses also exist, Zebra are wild relatives of horses. There are also wild and domestic donkies. Together the horses and their relatives are called equines. Wild horses (equines) evolved over more than 50 million years. 
- Dog Dogs have also been domesticated for a long time.