Canter Vs Gallop

 The canter is a controlled, three-beat gait performed by a horse. It is a natural gait possessed by all horses, faster than most horses' trot but slower than the gallop, and is used by all riders. The speed of the canter varies between 16–27 km/h (10–17 mph), depending on the length of the stride of the horse. A variation of the canter, seen in western riding, is called a lope, and generally is quite slow, no more than 13–19 km/h (8–12 mph).http://en.wikipedia.org/wiki/Horse_gait

The gallop is very much like the canter, except that it is faster, more ground-covering, and the three-beat canter changes to a four-beat gait. It is the fastest gait of the horse, averaging about 25 to 30 miles per hour (40 to 48 km/h), and in the wild is used when the animal needs to flee from predators or simply cover short distances quickly. Horses seldom will gallop more than 1 or 2 miles (1.6 or 3.2 km) before they need to rest, though horses can sustain a moderately-paced gallop for longer distances before they become winded and have to slow down

Cantering (English) or Loping (Western) is a three beat gait that goes:
Hind foot, other hind foot and opposite front at same time, then remaining front foot. If the left front foot hits last by itself the horse is said to be on the left lead, if the right strikes last by itself the horse is on the right lead. There is no suspension (hang time) in the air with a canter. The gait goes 1,2,3,1,2,3,1,2,3...

Gallop: 
Is a four beat gait (usually faster than canter/lope) that has a pause where no feet are touching the ground.
Right lead:
Left hind foot
Right hind foot
Left front foot
Right front foot
Pause with all feet up under the horse

Left lead is the opposite:
R hind
L hind
R front
L front 
Pause

The gallop goes: 
1,2,3,4, pause, 1,2,3,4, pause....

See below the Canter style :




See below the Gallop style:


Thanks to:
wiki
http://en.wikipedia.org/wiki/File:Gallop_animated.gif
http://en.wikipedia.org/wiki/Canter
http://en.wikipedia.org/wiki/Horse_gait