The Theravada school of Buddhism is the oldest and most orthodox segment of the Buddhist population. Unlike Mahayana Buddhists, the Theravada school maintains that enlightenment is reserved for a select group of religious figures and scholars. Borrowing heavily from the Hindu caste system, Theravada monks believe that the status that a person is born to is highly indicative of the state of that person's soul. Therefore it would be impossible for anyone other than an monk to even get close to enlightenment.
Another repercussion of their philosophy is the absence of the reoccurring Bodhisattva, or teacher figure. Because each person must reach the level of enlightenment on their own, there is no necessity for an educator figure. The one and only teacher, according to the Theravada tradition, is the Buddha himself. The Buddha is seen as a historical figure, not one of many in a continuing line. Those that reach enlightenment do so on their own merit without any aid from teachers or previously enlightened individuals, other than the historical Buddha.
Theravada theology derives from a strict interpretation of religious texts. They rely strongly on translations that are word for word, not extrapolated from generalizations. The Theravada sect is the less common sect throughout most of the world, and a minority influence in Vietnam.