Aura

Aura is the manifestation of our soul. It bears our burdens and shields our hearts.Aura is the manifestation of one's soul in the RWBY Universe, which can be used for a wide range of abilities depending on both the person and the amount of experience one possesses. Its appearance and the physical abilities it offers vary from person to person.

Semblance is an alternate term used to refer to some unique and innate abilities exhibited by certain individuals. How Semblance is related to Aura is not currently known, though it may be a specialised application thereof.

Description
Aura is an ability that all those with a soul can use, at least with enough practice. Because Aura is the manifestation of the soul, it can appear very differently depending on who is using it. For example, the color of Aura is different from person to person. Also, a person with a strong Aura may radiate brighter when using it.

It is mentioned that anything with a soul has an Aura, but humans seem to be the only beings able to weaponize it for their own protection. Skilled users of Aura can create their own barriers or even increase their own abilities in some way. Weapons can also act as a conduit for Aura, allowing for an even wider range for any attacks.

It has been shown that Aura strength degrades with continual use. This limits the applications of Aura in combat as, with time or heavy use, a person's Aura will decay to the point where they are left weakened or even incapacitated. This has been witnessed several times in the show: It is also likely that Ren's evident weakness in the latter part of the Beacon Academy Initiation test was due to his earlier heavy use of Aura, both defensively and offensively, against two King Taijitu.
 * When Pyrrha unlocked Jaune's Aura in The Emerald Forest;
 * When Jaune lost a duel with Cardin in Jaunedice.

Abilities
Aura is a necessary energy source for all Hunters, being their most powerful ally when in battle. Aura, as demonstrated by various characters, has the ability to do the following:
 * Heightened Perception: Aura seems to be able to sharpen one's senses, or allow one to detect danger, as mentioned by Pyrrha.
 * Defense: Demonstrated by Ren in the forest, and explained by Pyrrha. Aura is mainly used for defensive purposes. Ren used his to block the fangs of a King Taijitu that was attacking him.
 * Offense: Demonstrated by Ren in the forest, as he sends a shock wave of force propelling a fang through the snake's head, causing it to explode. Additionally Pyrrha has stated that all tools and equipment are conduits for a person's Aura.
 * Unlock Aura: One's Aura can be used to 'unlock' the Aura of someone else; as shown by Pyrrha, who unlocks Jaune's Aura. Doing this appears to take a toll on the user however.
 * Healing: It also seems that those with a strong enough Aura can heal minor wounds. Jaune used this directly on a small cut after having his Aura unlocked. However, it appears that the healing is automatic, and not caused at will. It also seems to wear off after engaging in combat, as Jaune's injuries returned post-battle with an Ursa.

Other specific abilities, known as semblances, appear to be unique to, or otherwise more pronounced, in certain individuals. Whether or not these abilities are classified as Aura applications is not known.

Activation
It appears that Aura is able to manifest in different ways when in use and takes on the color of one's inner energy. It appears as a slight glow around the body and also seems to be able to change eye color in certain people.

It has been stated that the activation of an Aura requires training and willpower, though someone with considerable training can unlock the Aura of another person.

Tournaments
In the episode Jaunedice, it is revealed that Aura strength, as a proportion of maximum potential, can be electronically monitored and displayed on a scroll. This has enabled the development of a competitive sport amongst Hunters and others.

Because Aura can protect its user against some of the force of physical blows, it is possible to duel using fully combat-ready weapons without risking death or serious injury. Such tournaments are closely monitored by a referee and, should a combatant's Aura strength fall below a certain red-line where they may no longer be sufficient to protect their users, the match is automatically halted and the combatant with this highest Aura percentile remaining declared the winner.

The duel between Jaune Arc and Cardin Winchester proves that Aura does not provide 100% protection against concussive blows as Jaune is visibly hurt and left winded by a blow to the abdomen from his opponent's mace. However, Glynda Goodwitch halts the match before Cardin can strike again, indicating that Jaune's Aura at about 20% power would not stop another full-strength blow.

There is at least one known major international competitive Tournament, the Vytal Festival, at which students at Beacon Academy are permitted to compete as representatives of Vale City-State. It is possible that the Mistral regional championship, won by Pyrrha three years in a row, is another Tournament but this has not yet been explicitly confirmed on-screen.

Known Aura Users

 * Lie Ren - Ren's Aura appears to be a shade of pink. His Aura allows him to make barriers and increase the force of his attacks. His pistols can also fire his Aura.
 * Pyrrha Nikos - So far Pyrrha has used her Aura to unlock Jaune's. Not much else is known about her Aura, but she is very knowledgeable about it. Her Aura is an intense red color.
 * Jaune Arc - After his Aura is unlocked, a cut on his cheek rapidly healed, and he also seemed to completely deflect a punch from Cardin Winchester. It is unknown what else his Aura can do, but Pyrrha notices that he has a lot of it. His Aura is white in color.

Trivia

 * It is stated by Pyrrha that only those who have souls are able to use Aura, meaning that creatures of Grimm are unable to use this ability as they lack a soul, and thus, an Aura.
 * People can have different colored Auras, possibly reflecting the type of soul they have. Pyrrha's looks red, Jaune's looks white, and Ren's appears to be a shade of pink.
 * It can be compared to Ki or Chi in other media.
 * How Aura differs from person to person is similar to how souls differ when seen in Soul Eater.
 * Aura being a manifestation of one's soul is similar in concept to AT Fields in Neon Genesis Evangelion.
 * In Jaunedice, it is revealed that one's Aura level can be measured in the form of a life bar. This is used in order to assess when a fighter is unfit for battle in a tournament battle, i.e. when the bar goes into the red.