Mahayana means "The Great Raft" or "The Great Vehicle. " It is the largest and most influential of the three main forms of Buddhism (the other two being Theravada and Vajrayana ). It is practiced in China, Japan and Korea. Vajrayana derived from it and shares many similarities with it. Mahayana emphasizes the idea of the bodhisattva over that of the arhat. The goal of an individual is therefore not to pass out of this world into nirvana, but to attain enlightenment--with the wisdom, understanding and power that goes with it--and then to show compassion by returning to this world to help those in need. Amitabha Buddha did this to establish Pure Land Buddhism. In comparison to Theravada, Mahayana Buddhism emphasizes the help that gods and bodhisattvas can give to people to help them escape samsara. It has elaborate descriptions of how this works and emphasizes prayers and rituals that enable people to seek this help. Zen is another branch of Mahayana Buddhism.