"It's where you scold someone."
Discipline are different things you can do while either riding or not riding a horse. There's English and Western disciplines. English disciplines would be Eventing - all three disciplines with Dressage, Cross-Country, and Show Jumping. Hunter-Jumper, Endurance, and Saddle Seat. Western disciplines would be Cutting, Barrel Racing, Cow Working Horse, and Roping. Disciplines while not riding on a horse would be Liberty, Halter, and Showmanship.
There's also different Horse Racing disciplines, Driving disciplines, Team disciplines, and Para-Equestrian disciplines. There's many other disciplines out there.
*I'm not sure if horse classes, including something called Flat classes, is another way to say horse disciplines, or they're complete opposite from one another. It's the one term I get confused on, and it doesn't help that those terms get switched around a lot*
