The school of meditative Mahayana Buddhism was introduced into China at around 520 by Indian monk Bodhidharma.
The Japanese Zen derives from Chinese Chan Buddhism and was introduced by Eisia.
The first technique comes from the Soto school and makes use of Zazen meditation.
The second comes from the Rinzai school and employs Koans, paradoxical question and answer dialogue.
The purpose is to lead to sudden, intuitive enlightment as the split between rational and irrational is transcended and the Buddha within is found.
Some of the questions in Zen are answered in silence.
Other questions are answered by repeating the question.
The paradox of Zen may be glimpsed by the following poem,
"When one looks at it, one cannot see it;
When one listens for it, one cannot hear it;
However when one uses it, it is inexhaustible.
Hands of Light: A Guide to Healing Through the Human Energy Field
ZEN QUOTES
Paralumun New Age Village