Ley

Live-giving
Ley is the natural power present in the air all over the world. Ley is what unicorns, pegasi, earth ponies, and many other species use to manipulate the world around them.

Only a few species can directly manipulate ley to perform their will.
 * Earth ponies use ley to cause plants, vegetation, and crops to grow at an incredible speed. The more skilled the earth pony, the faster the crop grows and the greater and better the yield.
 * Pegasi use ley to suspend themselves in the air and to accelerate. Their wings assist with that, but a pegasus' wings are mostly used to control their direction and to stop. The more skilled the pegasus, the faster they can go.
 * Unicorns use ley to cast an infinitely wide variety of spells. The more skilled the unicorn, the more powerful the spells they can cast, and for a longer time, or in a greater amount over a short time. Casting spells takes actual physical energy from a unicorn.
 * Other species can use ley to do many different things. For example, moose can use it to detect currents and drifts in water, and to sense what direction they are facing.

Ley is present all over the world, but it is focused in some areas more than others. The density of ley is far greater in Equestria than in most other land around the world, which is one of the smaller reasons Equestria is so successful.