Most groups are descended from the three major schools of Buddhism:
In the Buddhist countries of southern Asia, there never arose any serious differences on the fundamentals of Buddhism. All of these countries – Sri Lanka, Cambodia, Laos, Burma, and Thailand – have accepted the principles of the Theravada school and any differences there might be between the various schools are restricted to minor matters. The earliest available teachings of the Buddha are to be found in Pali literature and belong to the school of the Theravadins, who may be called the most orthodox school of Buddhism. This school admits the human characteristics of the Buddha, is characterised by a psychological understanding of human nature, and emphasizes a meditative approach to the transformation of consciousness. The teaching of the Buddha according to this school is very plain. He asks us to “abstain from all kinds of evil, to accumulate all that is good, and to purify our mind.” These can be accomplished by the Three Trainings: the development of ethical conduct, of meditation, and of insight-wisdom. The philosophy of this school is that all worldly phenomena are subject to three characteristics: they are transient, unsatisfactory, and without a substantial, permanent self. All compounded things are made up of two elements: a material and immaterial part. They are further described as consisting of nothing but five constituent groups – namely, the material quality and the four immaterial qualities: sensations, perceptions, mental formations, and consciousness. When that perfected state of insight, or Nibbana, is reached, that person becomes a “worthy person,” or Arhat. The life of the Arhat is the ideal for the followers of this school, a life where all (future) birth is at an end, where the holy life is fully achieved, where all that has to be done has been done, and there is no more returning to the worldly life.
The Mahayana is more of an umbrella body for a great variety of schools, from the Tantra school (the secret teaching of Yoga) well represented in Tibet and Nepal to the Pure Land sect, whose essential teaching is that salvation can be attained only through absolute trust in the saving power of Amitabha, longing to be reborn in his paradise through his grace, which is found in China, Korea, and Japan. Ch’an and Zen Buddhism, of China and Japan, are meditation schools. It is generally accepted that what we know today as the Mahayana arose from the Mahasanghikas sect who were the earliest seceders, and the forerunners of the Mahayana. They took up the cause of their new sect with zeal and enthusiasm and in a few decades grew remarkably in power and popularity. They adapted the existing monastic rules and thus revolutionized the Buddhist Order of Monks. Moreover, they made alterations in the arrangements and interpretation of the Sutra (Discourses) and the Vinaya (Rules) texts. They also rejected certain portions of the canon which had been accepted in the First Council. According to this, the Buddhas are lokottara (supramundane) and are connected only externally with the worldly life. This conception of the Buddha contributed much to the growth of the Mahayana philosophy. The ideal of the Mahayana school is that of the Bodhisattva, a person who delays his or her own enlightenment in order to compassionately assist all other beings and ultimately attains to the highest Bodhi.
This Buddhist tradition is predominant in the Himalayan nations of Tibet, Nepal, and Bhutan, and also in Mongolia. It is known as Vajrayana because of the ritual use of the vajra, a symbol of imperishable diamond, of thunder and lightning. At the center of Tibetan Buddhism is the religious figure called the lama, Tibetan for “guru,” which is also a source of another of its names, Lamaism. Several major lineages of lamas developed; the first, the Nyingma-pa, started in the ninth century. Two centuries later Sarma-pa divided into the Sakya-pa and the Kagyu-pa. Three hundred years later, one of Tibet’s revered lamas, Tsong-kha-pa, founded the reforming Gelug-pa.