Most horses move forward in four basic gaits: the walk, trot, canter and gallop. Riders more familiar with the Western style of riding--the kind movie cowboys do--may refer to the trot as the jog and the canter as the lope. But, no matter what they're called, it is easy to tell the difference between horse gaits if you know the basic mechanics.
Listen for the sound of the horse's hoofbeats if he is walking on hard ground. At the walk, the horse will be moving at his slowest gait. You should hear a distinctive four-beat rhythm and be able to count “one-two-three-four” as he moves. If he’s not held tightly by a rope or bridle, his head should move in a slight nod as he walks.
Watch the horse's legs. If a front leg and a back leg on the other side are moving together, he's trotting or jogging. A horse that’s trotting will move faster than a walk, at a rhythmic, swinging pace. His hooves will tattoo the ground in a distinctive two-beat clip-clop, as his legs move together in diagonal pairs. As one foreleg reaches out, the hind leg on the opposite side will reach forward. He may hover slightly in the air before those hooves touch the ground and the other two legs swing forward. At the jog, the legs move in the same pattern but at a slower pace than the trot, often just slightly faster than the walk.
Focus on the sound of hoofbeats and the pattern you can see, as the horse moves more quickly. If she's cantering, she'll seem to bound forward. Usually faster than the trot, the canter is a three-beat gait with a slight pause that occurs when all four hooves are off the ground for an instant. When a horse canters, one foreleg will “lead,” which means it lands on its own and slightly ahead of the other front leg. For instance, if a horse is leading with her right front leg, her hooves will hit the ground in this order: left hind; right hind and left front at the same time; right front; then a moment when all four hooves are off the ground. A horse that’s loping in proper form should follow the same sequence of hoofbeats, but at a less-animated, less-rollicking pace.
Look carefully to tell the difference between the canter and the gallop, the horse’s fastest pace. It's unlikely you'll be able to distinguish it by hearing the footfalls. There also are better clues than watching the sequence of leg movements, which is similar to those in the canter. A gallop is a four-beat gait, with the legs that landed together in the canter hitting the ground separately. During the gallop, though, the horse spends more time completely off the ground. In a picture, he may seem to be hovering. His stride is longer, and he may appear to become flatter across the top of his body and more elongated.