Buddha Nature is the already enlightened nature of all beings.
There are a few basic teachings that distinguish all forms of Mahayana and make it distinctive from Theravada. Here is a comparison of Mahayana and Theravada that make these distinctions clear.
Origins of Mahayana Buddhism
Mahayana's precise origins are a mystery, but it emerged as a separate school of Buddhism in about the 1st century BCE. Today it is the dominant form of Buddhism in China, Tibet, Japan and Korea.
In Mahayana Buddhism, the ideal of practice is to become a bodhisattva who strives to liberate all beings from the cycle of birth and death. The Bodhisattva Vows are vows taken formally by a Buddhist to do exactly that. The vows also are an expression of bodhichitta, the desire to realize enlightenment for the sake of others.
The early Mahayana school of Madhyamika focused on the nature of existence and becoming and on the teaching of shunyata, "emptiness." Madhyamika lives on today in Tibetan Buddhism, Ch'an (Zen) Buddhism, and other Mahayana schools.
Major Mahayana Sutras
The name sutra (Sanskrit for "thread") in Buddhism originally was given only to the sermons of the historical Buddha, as recognized by the First Buddhist Council (ca. 460 BCE). The works listed here probably were written between 100 BCE and 300 CE by unknown authors. Whatever their origin, they are considered to be sutras in Mahayana Buddhism.
Mahayana Web Links
Links to sites explaining several Mahayana Buddhist schools.
The Two Truths
The Two Truths Doctrine of Mahayana Buddhism explains the nature of reality.
Three Turnings of the Dharma Wheel
Mahayana Buddhists say the Buddha turned the dharma wheel three times. What are the three turnings of the wheel?
Sunyata, or Emptiness
Sunyata, or "emptiness," is a doctrine of Mahayana Buddhism that is widely misunderstood. What is "emptiness" and why is it important?