Zen
Zen is the Japanese branch of Mahayana Buddhism, derived from the Chinese Chán (which in turn comes from Indian Dhyana). Emphasizes meditation (zazen), direct experience over scriptural study, transmission "from mind to mind" via master-disciple lineage. Key concept: satori — sudden awakening.
Schools
Soto Zen — emphasis on prolonged sitting meditation (Dogen, 13th century). Rinzai Zen — emphasis on koans, paradoxical riddles to break dualistic thinking.