The real followers of the Buddha can practise this religion without adhering to any school or sect.
A few hundred years after the Buddha's passing away, there arose eighteen different schools or sects all of which claimed to represent the original Teachings of the Buddha. The differences between these schools were basically due to various interpretations of the Teachings of the Buddha. Over a period of time, these schools gradually merged into two main schools: Theravada and Mahayana. Today, a majority of followers of Buddhism are divided into these two schools.
Basically Mahayana Buddhism grew out of the Buddha's teaching that each individual carries within himself the potential for Buddhahood. Theravadins say that this potential can be realised through individual effort. According to Mahayanists, Bodhisattas are future Buddhas who, out of compassion for their fellow human beings, have delayed their own attainment of Buddhahood until they have helped others towards liberation. In spite of this basic difference, however, it must be stressed that doctrinally there is absolutely no disagreement concerning the Dhamma as contained in the sacred Tripitaka texts. Because Buddhists have been free to interpret the scriptures according to their understanding. But above all, both Mahayana and Theravada are one in their reverence for the Buddha.
The areas of agreement between the two schools are as follows:
Some people are of the view that Theravada is selfish because it teaches that people should seek their own salvation. But how can a selfish person gain Enlightenment? Both schools accept the three Yana or Bodhi and consider the Bodhisatta Ideal as the highest. The Mahayana has created many mystical Bodhisattas, while the Theravada believes that a Bodhisatta is a man amongst us who devotes his entire life for the attainment of perfection, and ultimately becomes a fully Enlightened Buddha for the well-being and happiness of the world.
The terms Hinayana (Small Vehicle) and Mahayana (Great Vehicle) are not known in the Theravada Pali literature. They are not found in the Pali Canon (Tripitaka) or in the Commentaries on the Tripitaka.
Theravada Buddhists follow orthodox religious traditions that had prevailed in India two thousand five hundred years ago. They perform their religious services in the Pali language. They also expect to attain the final goal (Nibbana) by becoming a Supreme Enlightened Buddha, Pacceka Buddha, or and Arahant (the highest stage of sainthood). The majority of them prefer the Arahantahood. Buddhists in Sri Lanka, Burma, and Thailand belong to this school. Mahayanists have changed the old religious customs. Their practices are in accordance with the customs and traditions of the countries where they live. Mahayanists perform their religious services in their mother tongue. They expect to attain the final goal (Nibbana) by becoming Buddhas. Hence, they honour both the Buddha and Bodhisatta (one who is destined to be a Buddha) with the same respect. Buddhists in China, Japan and Korea belong to this school. Most of those in Tibet and Mongolia follow another school of Buddhism which is known as Vajrayana. Buddhist scholars believe that this school inclines more towards the Mahayana sect.
It is universally accepted by scholars that the terms Hinayana and Mahayana are later invention. Historically speaking, the Theravada already existed long before these terms came into being. That Theravada, considered to be the original teaching of the Buddha, was introduced to Sri Lanka and established there in the 3rd century B.C., during the time of Emperor Asoka of India. At that time there was nothing called Mahayana. Mahayana as such appeared later, about the beginning of the Christian Era. Buddhism that went to Sri Lanka, with its Tripitaka and Commentaries, in the 3rd Century B.C., remained there intact as Theravada, and did not come into the scene of the Hinayana-Mahayana dispute that developed later in India. It seems therefore not legitimate to include Theravada in either of these two categories. However, after the inauguration of the World Fellowship of Buddhists in 1950, well-informed people, both in the East and in the West, use the term Theravada, and not the term Hinayana. In fact, the Samdhi Nirmorcana Sutra (a Mahayana Sutra) clearly says that the Sravakayana-Theravada and the Mahayana constitute one Yana (ekayana) and that they are not two different and distinct "vehicles". Although different schools of Buddhism held different opinions on the teaching of the Buddha, they never had any violence of blod shed for more than two thousands years. This is the uniqueness of Buddhist tolerance.