The main difference between Mahayana and Theravada Buddhism

In Theravada Buddhism, the ultimate goal is the attainment of the sublime state of nirvana, achieved by practicing the Noble Eightfold Path (also known as the Middle Way), thus escaping what is seen as a cycle of suffering and rebirth. Theravada has a widespread following in Sri Lanka and Southeast Asia.
Mahayana Buddhism, which includes the traditions of Pure Land, Zen, Nichiren Buddhism, Shingon, and Tiantai (Tendai) is found throughout East Asia. Rather than Nirvana, Mahayana instead aspires to Buddhahood via the bodhisattva path, a state wherein one remains in the cycle of rebirth to help other beings reach awakening. Vajrayana, a body of teachings attributed to Indian siddhas, may be viewed as a third branch or merely a part of Mahayana; Tibetan Buddhism, which preserves the Vajrayana teachings of eighth century India, is practiced in regions surrounding the Himalayas, Mongolia and Kalmykia. Tibetan Buddhism aspires to Buddhahood or rainbow body.”