Satori is the spiritual goal of Zen Buddhism (in Chinese: wu). Satori refers to individual Enlightenment, or a flash of sudden awareness. Satori is as well an intuitive experience. A brief experience of Enlightenment is sometimes called Kensho. Semantically, Kensho and Satori have virtually the same meaning and are often used interchangeably. In describing the Enlightenment of the Buddha and the patriarchs, however, it is customary to use the word Satori rather than Kensho, the term Satori involves a deeper experience. The feeling of Satori is that of infinite space.
The only way that one can "attain" Satori is through personal experience. The traditional way of achieving Satori, but not the only way, is through the use of Koans such as those found in the Gateless Gate, the Mumonkan.
Koans are "riddles" that students use to assist in the realization of Satori. The early Zen masters also used these words and phrases.
Another method of acquiring Satori is meditation. When they would meditate, they would become free of concepts and could enter the world of "suchness." Satori can be brought about through Zazen meditation. This meditation would create an objective self-associated awareness with a feeling of joy that overrides any other feelings of joy or sorrow.
Preparation for Satori can take a long time, but the actual experience is a very fast one. The length of training and the responsiveness of the individual determine the length of the Satori. The Zens training would begin with Satori, but there must be continuous Satoris as the learner keeps moving towards freedom. Total Enlightenment does not come until many Satoris of different depths have occured. When you go through Satori, and have this experience, you will no longer see the world in the same way. You will have a different perception of life; everything will be united into one non-dual whole. The final experience opens your mind to a new way of thinking and to a new being.
Satori is a key concept in Zen Buddhism. There can be no Zen without Satori. As long as there is Satori, Zen will continue to exist in the world.
Even though Satori is a key concept in Zen, it should be brought to your attention that Zen and its traditions do not have exclusive rights to the Enlightenment experience. That which is called Satori in Zen is a term that is wrapped around a phenomenon that "IS" and that is not "owned" by any group, religion, or sect. Many, many occurrences of that particular "phenomenon" have transpired both inside and outside the Doctrine of Buddhism.
The person who was to become the Sixth Patriarch in the Chinese Lineage of Ch`an was Enlightened as a young boy when he overheard a sentence being spoken from the Diamond Cutter Sutra. He had gone into town to sell firewood for his mother when he just happened to hear the line. Until that point in time he had not received any formal practice in meditation, nor was he versed in Buddhism to any great degree, if at all. The great Indian sage Bahgwan Shri Ramana Maharishi was a typical of his culture teenage boy when all of a sudden out of the blue he was Awakened to the Absolute. It is not just potential Zen masters in neither ancient China nor people in India that such events transpire. There are awakening experiences in the modern era as well, but even if those experiences are parallel to what is called Satori, they are not always called Satori. Formal religious orders, Sanga masters and gurus of various stripes do not particularly warm to such statements because of the undermining of their status, power, and positions.