Answer
Theravada Buddhism is the more conservative of the two major schools of Buddhist spirituality; the other slightly more popular form is Mahayana. The Theravada school is popular in Sri Lanka, Laos, Vietnam, Cambodia, and Thailand. Theravada Buddhism is distinguished from Mahayana mostly by its adherence to a particular set of written texts as their doctrinal authority. At the same time, most of the differences between Theravada and other schools of Buddhism could be defined by what those other schools believe “in addition to” what is taught in more conservative Buddhist traditions.
The key distinctive of Theravada Buddhism is its relatively narrow acceptance of certain Buddhist scriptures. Texts held in high regard by this school are written in the Pali language and are the oldest of all known Buddhist writings. The writings were created in Sri Lanka after Buddhist missionaries from India brought their faith to the island nation. These Sri Lankan written works are themselves based on centuries-old oral traditions. Unlike the sacred texts of faiths such as Christianity or Islam, the sacred texts of Theravada Buddhism are not considered to be infallible by those in the religion.
Another major difference between Theravada and other Buddhist schools is in upholding the monastic lifestyle as the best way of achieving enlightenment. In theory, Theravada accepts the idea that laymen can make great spiritual progress, but, in practice, only those who are committed to the monastic lifestyle have any reasonable hope of obtaining Buddha-hood. The divide between the monk and the layman in Theravada is much larger than it is in other Buddhist traditions.
According to Theravada Buddhism, one is only a “true” Buddhist when he desires to follow the Buddha (meaning both the figure of Gautama Buddha and the practitioner’s inner potential for enlightenment), commits himself to following the guidance of the Sangha (the worldwide family of Buddhist monks and nuns), and resolves to follow the Dhamma (the teachings of Buddha). Compared to the Mahayana school, Theravada places less emphasis on a concern for the enlightenment of others and a much higher emphasis on the importance of monks and the monastic lifestyle.
The core aspects of Buddhism, such as the Four Noble Truths and the Eightfold Path, are distilled in Theravada into seven core stages of spiritual purification. These begin with concepts such as finding the correct teacher, developing one’s meditation ability, and growing in one’s understanding of Buddhist truths.
As an ostensibly older, “leaner” form of Buddhism, Theravada is more easily defined in contrast to other Buddhist approaches. Most of what is taught in Theravada Buddhism has parallels in Mahayana schools, while the opposite is not necessarily true.