To ride the horses they have to be tacked up. The tack is the saddle, bridle and the other equipment that the horses wear during the race.
The saddle is the thing that you put on the horses back. It's made out of leather and it keeps the jockey on the horse. There are many different types of saddles, the kind used in racing is lightweight so that it doesn't slow the horse down. Also on the saddle is the stirrups. The stirrups are the rounded irons that the jockey puts his/her feet in, the stirrups are attached to the leather with thin pieces of leather called stirrup leathers. Under the saddle is a saddle pad. The saddle pad is a pad that protects the horse from getting saddle sores.
The bridle is a harness type piece of equipment. It's made out of pieces of leather, and there are many parts of a bridle. The nose band and the chin strap go around the horses nose, connected to those is the cheek strap and this is on either side of the face connected to that is the brow band the head band and the throat latch, wich go behind the ears, in front of the ears, and under the neck. The bit is a piece of metal that you put into the horses mouth, connected to the reigns which in what the riders use to control the horse.