It has the ability to sense the Auras of all things. It understands human speech.
(From Bulbapedia)Lucario is a bipedal, canine-like Pokémon, with fur that is predominantly blue and black. It possesses a short, round spike on the back of each forepaw, in addition to a third on its chest. It has red eyes, a long snout and ears. When its mouth is open, it has two pairs of pointed teeth, one in the upper jaw and one in the lower. It possesses cream-colored fur on its torso, and blue fur on its thighs that resembles shorts. It has a medium length tail of the same blue color as well. It stands on its toes rather than on its entire foot. It has developed four black appendages that hang down from its head, which rise when Lucario reads or manipulates aura, a special energy that it senses. Lucario can study this energy to predict the movements of their opponents and track their quarry. They also have the power to manipulate this energy in an offensive manner, in the form of explosive spheres of energy. Lucario can understand human speech, and have been reported to communicate with humans through telepathy.
(From Bulbapedia) Lucario appears to be based on the Egyptian god of funerals and the dead, Anubis, who has the head of an African golden wolf. Anubis's role in Egyptian mythology was to judge the hearts of deceased souls based on their actions during their life. This resembles Lucario's ability to see a life form's aura. It also seems to be based on an Egyptian boxer. Boxing is a sport that is believed to have origins in Egypt. The markings on Lucario's face resemble a mask. The rings around its shoulders may be inspired by iron rings used in martial arts. The four appendages on Lucario's head, together with the shape drawn by its mask (a bisected ring), may suggest inspiration from a khakkhara, which in popular depictions can respond to spiritual energies similarly to how Lucario's appendages act when it senses aura.
(From Bulbapedia) Lucario may be derived from the reverse of the Japanese transliteration of orichalcum (a mythical metal) or oracle (referring to its supernatural abilities involving aura). It may also involve lupaster (a subspecies of the Canis aureus), Cairo, pharaoh, lykos (Greek for wolf), luchar (Spanish for fight), or lucarius (Latin for (one) of light or luminary).