When you have your first contact with Buddhism (as someone from the west) there are numerous obstacles to overcome before any of it can start to make sense. The cultural trappings are very confusing because even though they all refer to it as Buddhism it looks very different on the surface based on where the Buddhist practice is occurring. Buddhism originated in India but it soon spread too many other cultures and countries. As it spread it was assimilated by each culture and in the process took on aspects of that cultures traditions. This meant that the practitioners took on the outward appearance of that culture in terms of dress or ritual objects. It also meant that in the process of converting to Buddhism each culture brought with it some aspects and teachings of their indigenous religions. Because of this it is confusing that when you study about Tibetan Buddhism and they talk about Tulku’s and then you study about Buddhism in Thailand there is no mention of them. The same is true in reverse where it is common for Thai Buddhist to have Spirit houses at their home or business but you do not see this in Japanese Buddhism. So the point to understand is that you are not losing your mind or is it even your fault for the confusion. The truth is that these things come from the indigenous religions of these countries and have been incorporated into their form of Buddhism. So whenever you see a discrepancy such as the Southeast Asian monks wearing saffron colored robes and the Japanese Zen monks wearing black robes the history of the development of Buddhism in that particular place is the reason. Lastly these are outward appearances for the most part and do not have much to do with the validity of the teaching itself. In terms of the spirit houses and Tulku’s although they are not common to all Buddhist lineages there is some argument in the Buddha’s teachings for their existence.
Since we are new to the Buddhist teachings as a whole these differences can be confusing but in reality we should not be that confused as there are definite parallels in our own traditions. If you look at the practice of Christianity across the world it very often appears different. If it wasn’t for the domination of the Catholic Church over the centuries it would appear even more diverse. At the time of Christ there were many different schools of Christianity with varying teachings of the meaning of God and Christ’s relationship to him. The practitioners of these different sects were all for the most part persecuted and their writings destroyed, when ever found, by the Roman Catholics starting during the time of Constantine. Luckily some evidence of these alternate views were found fairly recently with the discovery of the Dead Sea and the Nag Hammadi Scrolls. If we look at the ritual or even the church buildings of the sects that remained, the Catholics, Russian Orthodox, Greek Orthodox, and Protestants they vary greatly. The Lutherans, Seventh day Adventist, Methodist, Mormons, and Jehovah Witness all believe and follow Jesus Christ but each has its own teachings that the others do not follow. These differences came about as the teachings of Christ spread across the world and were assimilated by the various cultures where it took hold. There were also different individuals that started new sects because of disputes with the establishment or the desire to emphasize some aspect that the establishment found heretical. One difference is that on a whole, with a few exceptions, Buddhist from the various sects do not view the others as heretical. Usually the different denominations are seen as just a different path to the same goal. There are though differences in the way the different schools view the efficiency of their own path in relation to the others.
The oldest member of the different “Yanas” (Path or Vehicle) is the Hinayana. This is comprised of most of the schools located in Southeast Asia and Sri Lanka. This group of schools follow the Pali scriptures that were canonized after the first Buddhist council (about 483 b.c.) following the Buddha’s death. At this council Ananda had been the chief reciter of the teachings (Dhamma) and Upali the principle reciter of sermons on conduct, discipline and the monastic rules (Vinya). Hinayana means the “smaller” or “lesser” vehicle. This is a very misleading title especially if you have ever read any of Ajahn Chah’s writings! Ajahn Chah is a follower of Theravada (The way of the Elders) Buddhism. He taught in a very simple style that was very easy, if you were not paying very close attention, to miss how incredibly profound his teaching was. The reason for the term “lesser” was that these monks aspired to be Arahants or Arhat (one who has attained enlightenment). The difference between and Arahant and a Buddha is that a Buddha attains Enlightenment by himself where an Arahant does so by following someone else’s teaching. The Buddha is also referred to at times as an Arahant in the Pali scriptures. Another name for these early forms of Buddhism is Sravakayana or the “Vehicle of the Hearers”. It was generally thought by the Hinayanist that to become a Buddha would take many lifetimes. Typically on Hinayana Buddhist altars you will only find images of Shakyamuni, the historical Buddha.
The next “Yana” is the Mahayana or Greater Vehicle. The second Buddhist council (about 383 b.c.) was called to eliminate some unauthorized practices. At the same time a group of 10,000 called the Mahasanghikas had a meeting to oppose the orthodox elders. This was basically the beginning of the Mahayana movement. By about 70 a.d. the Mahayana was beginning to be formed into what it was later known for. One difference from the Hinayana was that the Mahayana commentaries and other writings were written in Sanskrit instead of Pali. Sanskrit was the religious language of India that the Brahman used, sort of akin to Latin in the west, where as Pali was more of a common language that the average person would understand. There were scriptures written in Sanskrit such as the Lotus sutra and the Avatamsaka sutra that the Mahayanist followed. The Mahayana emphasized the teaching of Compassion (Karuna) and Wisdom or Insight (Prajna). One big difference is the Mahayana ideal of Bodhisattva instead of the Arahant. The Mahayanist thought that the Arahant was somewhat selfish in that they strived for Enlightenment for themselves individually. The Bodhisattva took the Bodhisattva vow to not obtain complete Enlightenment until all other sentient beings have also obtained it. The Zen and Pure Land styles of Buddhism are included in the Mahayanna schools. It was still thought that becoming a Buddha could take many lifetimes but sudden enlightenment was possible. In the Mahayana schools they started to adopt many Buddha’s and Bodhisattvas from Hinduism. So on a Mahayanna altar you will often find images of Amitabha (Amida), Avaloketeshivara (Kannon, Kwan Yin), Manjusuri (Monju), or Ksitigarba (Jizo). These are thought to represent different aspects of Enlightenment, Avaloketeshivara representing Compassion and Manjusuri representing Wisdom for example.
The last “Yana” is the Vajrayana or Diamond vehicle. It is Vajrayana tradition that the Indian monk Nagarjuna was the first master of the Esoteric teachings. The name is derived from the image of a Thunderbolt (Vajra) which symbolized the imperishable nature of Enlightenment. It also represents the indivisibility of Emptiness (Shuyata), Compassion (Karuna), and Wisdom (Prajna). This form of Buddhism is also referred to as Tantric Buddhism. One of the differences in their thought was the idea of a Conventional (Exoteric) and Absolute or Ultimate (Esoteric) truth. They believed that some teachings merely pointed you toward an ultimate truth but they were not the ultimate truth itself. The Vajrayanist followed the Tantra’s such as the Vajra-sekhara Tantra (Diamond Pinnacle Tantra) and the Maha-Vairocana-abhisambodhi Tantra (Tantra of the Awakening of Maha-Vairocana). Another new concept was that of the Primordial or Cosmic Buddha which in the Maha-Vairocana-abhisambodhi Tantra was represented by the Buddha Vairocana. The Vajrayana schools teach the Three Mysteries Body (Mudra), Speech (Mantra), and mind (Visualization) and that you can obtain Buddhahood in this very life. Lastly these school use Mandalas, for visualization and meditation, which are a symbolic representation of the Universe. Most Tibetian schools fall into this category as well as the Tendai and Shingon schools in Japan.
This was just a brief introduction to the three major classifications of Buddhist schools. There are many schools that fall under each and much more to study about all of them. So hopefully this brief outline will help next time you see some reference to one of the “Yana’s”.