Eventing (also known as horse trials and the Equestrian Triathlon) is an equestrian event where a single horse and rider combination compete against other horse and rider combinations across the three disciplines:
Most people don't know the roots of Eventing came from the Calvary. Originally, Horse Trials took its name from the comprehensive cavalry test given to ensure mastery of several types of riding.
This equestrian triathlon was first introduced to the Olympics in 1902.
The competition may be run as a one-day event (ODE), where all three events are completed in one day (dressage, followed by cross country and then stadium) or a three-day event (3DE), which is more commonly now run over four days, with dressage on the first two days followed by cross country the next day and then show jumping in reverse order on the final day. Eventing was previously known as Combined Training, and the name persists in many smaller organizations. The term "Combined Training" is sometimes confused with the term "Combined Test" which refers to a combination of just two of the phases, most commonly dressage and show jumping.