All Buddhist schools or branches embrace a doctrine of karma and reincarnation, but they apply it differently. Theravada Buddhists tend to emphasize the importance of gaining merit (through virtuous behavior, the support of monks and temples, and so on) in order to be reborn in a higher state, with the eventual goal of extinguishing all karma and entering nirvana. Mahayana Buddhism, by contrast, focuses on the ideal of the bodhisattva, a being who has reached enlightenment but chooses not to enter nirvana until all beings can do so. Tibetan Buddhism—also sometimes called Vajrayana Buddhism—accords with the Mahayana emphasis on the bodhisattva but modifies it in several important aspects. For example, only Tibetan Buddhism uses the practice of identifying tulku lineages, in which one teacher is immediately succeeded by his own reincarnation. In some instances, the tulku is understood to be the embodiment of a bodhisattva; the Dalai Lama embodies Avalokitesvara, the bodhisattva of compassion.