Theravada (pronounced “terraVAHduh”), the “Doctrine of the Elders,” is the only survivor among the early schools of Buddhism, and is generally regarded as the oldest, most orthodox, and most conservative form of Buddhism. It is relatively uninfluenced by other indigenous belief systems. It is believed to have survived intact from the 500 Elders, who followed in the tradition of the monks of the first Buddhist Council.
Theravada has no hierarchical authority structure, though seniority is respected in the sangha. It accepts the Pali canon (see Tripitaka) as the authoritative scripture that contains the complete teachings of the Buddha. Within four centuries after the Buddha there were 18 schools of Buddhism. All of those traditions are now extinct except for the Theravada.
The Mahayana doctrine began around 50 BC but it was not taught by the Buddha and it contradicts the Buddha’s teachings. Tibetan and Zen Buddhism are a part of the Mahayana. Today Theravadin monks feel that they represent the Buddha as He would have wished. In order for you to best follow the Buddha’s teachings as the Buddha would have wanted you to, you should study and practice the Theravada path which is a living tradition with an unbroken lineage going back to the historical Buddha himself.
Mahayana Buddhism contains much of the Buddha’s teachings but it is mixed with other philosophical beliefs so that it has a different view leading to a different goal. Theravadins revere the historical Buddha but do not recognize the various celestial buddhas and ancillary gods associated with Mahayana Buddhism.
For many centuries, Theravada Buddhism has been the predominant religion of continental Southeast Asia (Thailand, Myanmar/Burma, Cambodia, and Laos) and Sri Lanka; today Theravada Buddhists number over 100 million worldwide. In recent decades Theravada has begun to take root in the West.