Pure Land Buddhism (zh. 浄土宗), also known as Amidism, is a branch of mainstream Mahayana Buddhism and presently the most popular school of Buddhism in Asia.
Pure Land Buddhism is based upon the Pure Land sutras first brought to China circa 150, which describe Amitabha, an ancient Buddha. This concept, personified or otherwise, can be translated variously but is usually shortened to "Amituo" or "Amitofo" in Chinese (阿彌陀佛), "Amida" in Japanese and "Amito" in Korean.
Although the Infinite Life Sutra, or Longer Pure Land Sutra, was translated in to Chinese by the royal Kuchean monk Po-Yen as early as 258, the Pure Land school first became prominent with the founding of a monastery upon the top of Mount Lushan by Hui-yuan in 402. It spread throughout China quickly and was systematized by Shan-tao (613-681). The philosophy spread to Japan and slowly grew in prominence. Honen Shonin (1133-1212) established Pure Land Buddhism as an independent sect in Japan, known as Jōdō Shu. Today Pure Land is the dominant form of Buddhism in Japan.
Contemporary Pure Land traditions see the Buddha Amitabha preaching the Dharma in his buddha-field (sa. buddhakchetra), called the "Pure Land" or "Western heaven" (西天), a region offering respite from karmic transmigration. In such traditions, entering the Pure Land is popularly perceived as equivalent to the attainment of nirvana.
In fact, the main idea behind Pure Land Buddhism is that nirvana is no longer practical nor possible to attain in our present day. Instead, devotion to Amitabha will gain one enough karmic merit to go to the Pure Land (reminiscent of Heaven) from which Nirvana will be easier to attain, because in this paradise there are no negative experiences so no new negative karma is created. Existing negative karma would disappear.
Some Pure Land Buddhists have taught that in order for a devotee to be reborn in Amitabha's Western Paradise, they should chant or repeat a mantra or prayer to Amitabha as often as possible to reinforce a proper and sincere state of mind. This fairly simple form of veneration has contributed greatly to its popularity.
Eastern Pure Land
In esoteric Vajrayana Buddhism, Amitabha's Western Pure Land has a counterpart in Akshobhya's Eastern Pure Land: Abhirati. While recognized especially by the Japanese Shingon sect, the Eastern Pure Land is not the object of popular veneration in the same manner as the Western Pure Land.