Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha (Pali/Sanskrit "the awakened one"). The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th centuries BCE. He is recognized by Buddhists as an awakened or enlightened teacher who shared his insights to help sentient beings end ignorance (avidya) of dependent origination, thus escaping what is seen as a cycle of suffering and rebirth.
Two major branches of Buddhism are recognized: Theravada ("The School of the Elders") and Mahayana ("The Great Vehicle"). Theravada has a widespread following in Sri Lanka and Southeast Asia. Mahayana is found throughout East Asia and includes the traditions of Pure Land, Zen, Nichiren Buddhism, Tibetan Buddhism, Shingon, Tiantai (Tendai) and Shinnyo-en. In some classifications Vajrayana—as practiced mainly in Tibet and Mongolia —is recognized as a third branch, while others classify it as a part of Mahayana. The are other categorisations of these 3 Vehicles or Yanas.
While Buddhism remains most popular within Asia, both branches are now found throughout the world. Estimates of Buddhists worldwide vary significantly depending on the way Buddhist adherence is defined. Lower estimates are between 350–500 million.
Buddhist schools vary on the exact nature of the path to liberation, the importance and canonicity of various teachings and scriptures, and especially their respective practices. The cardinal doctrine of dependent origination is the only doctrine that is common to all Buddhist teachings from Theravada to Dzogchen to the extinct schools. The foundations of Buddhist tradition and practice are the Three Jewels: the Buddha, the Dharma (the teachings), and the Sangha (the community). Taking "refuge in the triple gem" has traditionally been a declaration and commitment to being on the Buddhist path and in general distinguishes a Buddhist from a non-Buddhist. Other practices may include following ethical precepts, support of the monastic community, renouncing conventional living and becoming a monastic, the development of mindfulness and practice of meditation, cultivation of higher wisdom and discernment, study of scriptures, devotional practices, ceremonies, and in the Mahayana tradition, invocation of buddhas and bodhisattvas.
Source: Wikipedia, "Buddhism", available under the CC-BY-SA License.