Since its origin more than 2,000 years ago, Mahayana Buddhism has diverged into many schools with a vast range of doctrines and practices.
It is difficult to make any blanket statements about Mahayana that hold true for all of Mahayana. For example, many Mahayana schools offer a devotional path for laypeople, but others are primarily monastic. Some are centered on a meditation practice, while others have replaced meditation with chanting and prayer.
To define Mahayana, it is useful to understand how it is distinctive from the other major school of Buddhism, Theravada.
The Enlightenment of All Beings
While Theravada emphasizes individual enlightenment, Mahayana emphasizes the enlightenment of all beings. The Mahayana ideal is to become a bodhisattva who strives to liberate all beings from the cycle of birth and death.
Beneath the bodhisattva ideal is an understanding of the doctrine of anatman -- the nature of the self -- that differs from that of Theravada. Very basically, Theravada considers anatman to mean that an individual's ego or personality is a fetter and delusion. Once freed of this delusion, the individual may enjoy the bliss of Nirvana.
Mahayana, on the other hand, considers all physical forms to be void of intrinsic self (a teaching called shunyata, which means "emptiness") and individual autonomy to be a delusion. Therefore, according to Mahayana, individual enlightenment is not possible. The ideal in Mahayana is to enable all beings to be enlightened together, not only out of a sense of compassion, but because we cannot separate ourselves from each other.
Connected to shunyata is the teaching that Buddha-nature is the immutable and eternal nature of all beings, a teaching not found in Theravada. Exactly how Buddha-nature is understood varies somewhat from one Mahayana school to another. Some explain it as a seed or potential; others see it as fully manifested but unrecognized because of our delusions.
The Mahayana doctrine of the Trikaya says that each Buddha has three bodies. These are called the dharmakaya, sambogakaya and nirmanakaya. Very simply, dharmakaya is the body of absolute truth, sambogakaya is the body that experiences the bliss of enlightenment, and nirmanakaya is the body that manifests in the world.
Another way to understand the Trikaya is to think of the dharmakaya as the absolute nature of all beings, sambogakaya as the blissful experience of enlightenment, and nirmanakaya as the embodiment of dharmakaya in human form.
Most schools of Mahayana acknowledge the Tripitaka to be a collection of the teachings of the historical Buddha. However, Mahayana has developed a large canon of sutras and other texts that Theravada does not recognize as legitimate. Not all Mahayana sutras are recognized by all Mahayana schools, however.
Mahayana literature features myriad iconic characters generally missing from Theravada literature. These include bodhisattvas, demons, protective divinities, and various spirits, plus the transcendent (dharmakaya and sambogakaya) and earthly (nirmanakaya) Buddhas (see The Triyaka, above).
Pali Versus Sanskrit
Mahayana Buddhism uses the Sanskrit rather than the Pali form of common terms; for example, sutra instead of sutta; dharma instead of dhamma.
A Note on Vajrayana
Vajrayana is a school of Buddhism that combines elements of Hindu yoga with Buddhist teachings. It is most closely associated with Tibetan Buddhism. Sometimes Vajrayana is presented as a third vehicle along with Theravada and Mahayana. However, all of the features of Mahayana listed above also apply to Varjayana. For that reason, Vajrayana is most often considered a variation or extension of Mahayana.