Mahayana (lit. Great Vehicle) is one of two major schools of Buddhism. Followers originate in China, Japan, Korea, and a decent portion of adherents in Vietnam and Taiwan. From Mahayana developed the Vajrayana which combines all previous schools.
The way of the Mahayana, developed from the earlier and more austere Theravada school of Buddhism, tends to be characterized by a greater emphasis of the supernatural. These include from celestial realms and powers, to a spectrum of Bodhisattvas, both human and seemingly godlike, who can assist believers.
The large number of Bodhisattvas and the combined inviting nature within Mahayana doctrine allows the religion to be extremely syncretic. For example, Taoism existed within China before the arrival of Buddhism, and metaphysically, there are important distinctions between the two. However, the structure of Mahayana Buddhism allows it to simply absorb Taoists deities as other bodhisattvas. Similarly, it is common for practictioners of Mahayana Buddhism to regard Confucius, Jesus Christ and Muhammed as simply other bodhisattvas allowing those religions to fit within the context of Buddhism.
Mahayana Buddhism, at its core, regards such ideas as artful means of bringing people closer to enlightenment. Bodhisattvas are the ultimate practioners of this approach. Although unenlightened by refusing Nirvana, they remain in the physical plane - the realm of illusion (Maya). Their purpose is to guide other beings on their path to enlightenment.
As an example, it is unlikely that a drunkard will, without assistance, achieve enlightenment. A Bodhisattva may appear to such a person as a fellow drunkard. Over time, the Bodhisattva will guide that person to a path that will lead them closer to Nirvana - often without the beneficiary ever realizing what has happened or why.
Mahayana Buddhism is characterized by a tradition of statue representations of Buddhas. This tradition as an offshoot of the Greek statues which was carried into central Asia by Alexander the Great. Early representions of Buddhas are known as Greco-Buddhist statues and are clearly modelled after Greek statues. This tradition was later carried east from Afghanistan into India, China and Japan.
Soothill says: "Mahāyāna; The great yāna, wain, or conveyance, or the greater vehicle in comparison with the Hīnayāna. It indicates universalism, or Salvation for all, for all are Buddha and will attain bodhi. It is the form of Buddhism prevalent in Tibet, Mongolia, China, Korea, Japan, and in other places in the Far East. It is also called Northern Buddhism. It is interpreted as the greater teaching as compared with the smaller, or inferior. Hīnayāna, which is undoubtedly nearer to the original teaching of the Buddha, is unfairly described as an endeavour to seek nirvana through an ash-covered body, an extinguished intellect, and solitariness; its followers are śrāvakas and pratyekabuddhas (i.e. those who are striving for their own deliverance through ascetic works). Mahāyāna, on the other hand, is described as seeking to find and extend all knowledge, and, in certain schools, to lead all to Buddhahood. It has a conception of an Eternal Buddha, or Buddhahood as Eternal (Adi-Buddha), but its especial doctrines are, inter alia, (a) the bodhisattvas, i.e. beings who deny themselves final Nirvana until, according to their vows, they have first saved all the living; (b) salvation by faith in, or invocation of the Buddhas or bodhisattvas; (c) Paradise as a nirvana of bliss in the company of Buddhas, bodhisattvas, saints, and believers. Hīnayāna is sometimes described as self-benefiting, and Mahāyāna as self-benefit for the benefit of others, unlimited altruism and pity being the theory of Mahāyāna. There is a further division into one-yana and three-yanas: the trīyāna may be śrāvaka, pratyeka-buddha, and bodhisattva, represented by a goat, deer, or bullock cart; the one-yāna is that represented by the Lotus School as the one doctrine of the Buddha, which had been variously taught by him according to the capacity of his hearers. Though Mahāyāna tendencies are seen in later forms of the older Buddhism, the foundation of Mahāyāna has been attributed to Nāgārjuna. "The characteristics of this system are an excess of transcendental speculation tending to abstract nihilism, and the substitution of fanciful degrees of meditation and contemplation (v. Samādhi and Dhyāna) in place of the practical asceticism of the Hīnayāna school."[Eitel 68-9.] Two of its foundation books are the Awakening of Faith and the Lotus Sutra but a large number of Mahāyāna sutras are ascribed to the Buddha."