Dressage is defined by the International Equestrian Federation as "the highest expression of horse training." Competitions are held at all levels from novice to the World Equestrian Games. Its fundamental purpose is to develop through  progressive training methods, a horse's natural athletic ability and willingness to perform, thereby maximizing its potential as a riding horse. At the peak of a dressage horse's gymnastic development, the horse will respond promptly to a skilled rider's minimal aids. The rider will be relaxed and appear effortless while the horse willingly performs the requested movement. In modern dressage competition, successful training at the various levels is demonstrated through the performance of "tests", a prescribed series of movements ridden within a standard arena. Judges evaluate each movement on the basis of an objective standard appropriate to the level of the test.

A dressage saddle is required. It is an English-style saddle with a long, straight saddle flap, a deep seat and usually a pronounced knee block. Dressage saddles have longer girth points and use a shorter girth than other types of English saddles, to minimize the bulk under the rider’s leg.  A dressage saddle is required in FEI classes, although any simple English-type saddle may be used at the lower levels.

At the lower levels of dressage, a bridle commonly includes a cavesson  noseband, with a flash or drop noseband being permitted. At the upper levels a plain cavesson is used on a double bridle.

The dressage horse at lower levels is only permitted to be shown at recognized competitions in a snaffle bit, though the detail regarding bitting varies slightly from organization to organization. The loose-ring snaffle with a single- or double-joint is most commonly seen. Upper level and FEI dressage horses are shown in a double bridle, using both a bradoon and a curb bit with a smooth curb chain.  The FEI rules of dressage lay down what bits may or may not be used and it is best to consult these rules and the rules of the presiding organisation when selecting a bit.