As Buddhism traveled from India into other parts of Asia after the Buddha's death, it interacted with the existing spiritual and philosophical traditions of those countries - mostly Bon in Tibet, Taoism and Confuciounism in China, and Shinto in Japan - influencing the new schools of Buddhism as they formed in each area. In India, Buddhist teachings also interacted with kundalini yoga traditions, which now share many energy-based practices with Vajrayana Buddhism . Although core teachings such as the Four Noble Truths and Eightfold Noble Path are at the heart of all branches of Buddhism, the meditation forms, scripture, and teaching styles vary quite a bit between schools.
Many different Buddhist teachings made their way to Japan, and have resulted in several thriving Buddhist branches there. The four main schools of Buddhism in Japan today are Amidist or Pure Land Buddhism, Nichiren Buddhism, Shingon Buddhism and Zen Buddhism. All four are considered Mahayana Buddhist branches, which formed after Theravada Buddhism, and are focused on the bodhisattva ideal of attaining enlightenment for the benefit of all sentient beings.
Pure Land or Amidist Buddhism is focused on Amitabha Buddha, a Buddha within Mahayana described in the Sukhavativyuha and Amitayurdhyana sutras. Sometimes referred to as the 'Infinite Light' Buddha, or the 'Buddha of Infinite Light', these sutras describe Amitabha's many meritorious deeds and devoted spiritual practice in past lives. Amitabha is now said to reside in the 'Pure Land' or 'Buddha Fields', which practitioners may visit themselves through devoted practice. Although it varies in different Pure Land schools, practice usually involve meditating on Amitabha Buddha and chanting mantras associated with him. Upon achieving enlightenment, a practitioner enters the Pure Land for further spiritual instruction, and then has the choice to remain there or return to any of the six realms of existence to help others attain enlightenment.
Nichiren Buddhism is based on the teachings of the 13th century Japanese monk Nichiren. Centered almost completely on the Lotus sutra, it focuses on the ability of anyone to achieve enlightenment in one lifetime. While alive, Nichiren felt that other branches of Japanese Buddhism had deviated from this core teaching of the Lotus sutra. The central practice of Nichiren Buddhism is the chanting of the Daimoku, 'Namu Myoho Renge Kyo'. The purpose of this chant is to devote oneself fully to the teachings of the Lotus Sutra, and attain awakening in one lifetime through it.
Both Nichiren and Pure Land Buddhism were originally branches of Tendai Buddhism, an esoteric Buddhist branch with many Shinto roots. Although still practiced today in Japan, these two descendants of Tendai Buddhism have grown larger over time.
Shingon Buddhism developed at the same time as Tendai, and shares many of its esoteric roots. Shingon is considered a form of Vajrayana Buddhism one of the few non-Tibetan forms and therefore centers on energy practices, mandalas, esoteric transmission, and the teacher-student relationship. The 4 main tantras - writings on esoteric practices of Shingon are the Mahavairocana Tantra, the Vajrasekhara Sutra, the Adhyardhatik Prajiramita Sutra, and the Susiddhikara Sutra (all are now considered tantras although they have 'sutra' in their titles.) These tantras are also recognized by Indian and Tibetan branches of Vajrayana Buddhism, although most of those schools have other tantras that developed or surfaced later.
Shingon rituals and practices revolve around two mandalas, of the 'Womb Realm' and the 'Diamond Realm'. Like all esoteric or Vajrayana Buddhism, Shingon teaches that enlightenment can be transmitted or communicated through meditation practices and ceremonies involving mandalas, mudras, mantras and other physical representations of enlightened awareness.
Zen Buddhism is the form of Japanese Buddhism perhaps best known to Westerners. According to legend, the Indian monk Bodhidharma brought Zen teachings to Japan in the 5th/6th century, after studying Zen's Chinese precursor, Chan Buddhism, in China for many years. Zen emphasizes direct realization, or satori, in the awakening process. Intellectual or conceptual knowledge is de-emphasized, as are the energy practices associated with some other Mahayana schools. The two main schools of Buddhism in Japan today are Soto and Rinzai, with a smaller school known as Obaku also still practiced. Rinzai Zen is known for its use of koans as triggers for satori, while Soto focuses more on breath and mindfulness based zazen (meditation), and the integration of practice with daily life.