Aura (Japanese: 波導 wave-guiding) is a form of spiritual energy introduced in Lucario and the Mystery of Mew. It is described as the essence of every living creature.
In the past there were Aura Guardians that can senses and control it's power while doing good deeds also they pass on the skills if they posses the same power as well. Although the Aura Guardians disappear from history there are only Riley and Ash in the present time who can use Aura powers and abilities, though Ash chose to continue his Pokémon training.
Abilities of Aura
Aura Guardians have the ability to sense other Aura as well there surroundings, even if they can't see, also they can transfer Aura to others, however those abilities can be risky. They create barriers and attacks with Aura to protect others or defend them selfs. Aura Guardians can activate Time Flowers also they can read minds and actions from others around them.