Buddhism like most other religions has several different divisions or branches of philosophy.
The two main divisions of Buddhism are Theravada (Hinayana) and Mahayana Buddhism.
Theravada Buddhism is considered the orthodox school. It is considered to be truer to Gautama Buddha’s teachings than Mahayana. Theravada was the original school of Buddhist philosophy. Its scriptures are in Pali, the language that Buddha taught in. At present, Theravada Buddhism is to be found in Sri Lanka, its main bastion, and also in Myanmar, Thailand and other parts of South East Asia.
Mahayana Buddhism is the heterodox school of Buddhist philosophy. Its scriptures are in Sanskrit, the language of Indian scholasticism. It originated later than Hinayana. At present, Mahayana Buddhism is to be found in Japan, China and other Asian countries.
The terms ‘Mahayana’ and ‘Hinayana’ were given by the Mahayana school. Mahayana means the Greater path and Hinayana the Lesser path, so although the Hinayana schools were earlier than the Mahayana and the more orthodox, they were given an inferior name which has unfortunately stuck. The Mahayana texts describe 18 different schools under the Hinayana branch, but of these only the Theravada school is extant today.
The two divisions differ in their philosophy right from their Metaphysical definitions, on their Ontology. Theravada follows Realistic ontology whereas Mahayana follows Idealistic ontology.
Gautama Buddha in his teachings had not defined any metaphysical position. The Buddha’s heart was filled with compassion for his fellow beings, and the goal of his teachings was to relieve us of our suffering. For this, metaphysical speculation is not necessary, and in fact it can be harmful by keeping us engaged in conjectures and arguments.
Buddha compared it with a man who has an arrow stuck in his chest. It is not necessary now to know the length and breadth of the arrow or what wood it is made of. The important thing is to get the arrow out. So also in religion, the main thing is to lead a life that will guide us out of sorrow and not to indulge in metaphysical dialogues.
Thus arose the forbidden questions of Buddhism, the 62 banned metaphysical questions. Buddha expressly forbade that these questions should be asked. The questions all relate to metaphysical queries, like whether the world exists or not, whether the soul exists or not, etc. In the pure form taught by Buddha, these questions are considered harmful and the true aspirant is forbidden to engage his or her mind on these questions.
But the normal human being, and specially in a country like India where philosophical speculation is so important, can hardly forbear from metaphysical speculation. Immediately after the Buddha’s death, his disciples began to define metaphysical positions on various aspects. This was done mainly in three ‘Sanghas’ or large conclaves held after his death, and in these Sanghas it was finally realized that there was a schism in Ontological definitions and there was a split in Buddhism.
The Buddha had abstained from making any metaphysical commitment. But his teachings contained two important points. He had said that ‘Dukkha exists’ and that ‘Dukkha is not permanent’. From these two teachings, his disciples fashioned their whole metaphysical position.

Theravada Buddhism

Theravada Buddhism begins from Realistic ontology. In this the trio of thinker, thought and the–thing–known, ie. the object, are taken to exist independently and simultaneously. Both the subject and the object exist independently, the object is not just a dream of the subject.
But the object, the world, does not have absolute reality. The world in Theravada has only dependent reality. One thing is dependent on another for its existence, thus milk is changed to curds and curds to cheese and so on, without anything having an absolute reality or existence. There is no absolute in this world, the whole world exists in this flux of dependent reality. The world is relative reality through and through. This state of existence of the world in dependent reality is called pratitya-samutpada.
The spiritual goal is to realize this, that the world is just a flux of unreality. With this realization, the Buddhist aspirant can be free from desire which springs from clinging to the world, and with the cessation of desire, the aspirant will also be free from dukkha or suffering. In this way, he or she will attain the stage of absolute calmness and dispassion of an Arhat, and attain Nirvana or liberation. This is the final goal of Theravada Buddhism.

Mahayana Buddhism

Mahayana Buddhism begins from Idealistic ontology.
In Idealistic ontology, the aspirant begins from considering the ‘I’, the subject, to have the first independent existence. The ‘I’ or individual consciousness is taken as the standpoint from which the world is analyzed, instead of the trio of the ‘I’, thought, and the object as in Realistic Ontology.
Once we take the ‘I’ or consciousness alone, we realize that the world is but a projection or picture in the mind of the ‘I’. We know that the mind can also have dreams, which we know to be untrue. Thus we cannot prove the reality of the world, and we are forced to say that the world may have no more reality than a dream, in other words, that the world does not exist at all in reality and the only existence is that of the subject, our ‘I’.
Based on this metaphysics/ontology, Mahayana Buddhism has three schools.

Sautantrika

Sautantrika is the first school of Mahayana Buddhism. In Sautantrika, the position of Idealism is taken up first, but then instead of going on to say the world is unreal, Sautantrikas affirm the reality of the world through inference. Although there is no way to know whether the world exists or not in Idealistic ontology, the Sauntantrikas say that since practically we see the world around us and have experiences in it, we can infer the existence of the world from practical experience.
Taking this position, the rest of the teaching follows the Theravada path, with the world said to be a dependent reality only and Nirvana being a realization of this truth.
There is no major school of Sautantrika philosophy extant today, and it is of historical importance only.
Sautantrika is usually described as a Hinayana school, but given that it begins from an Idealistic ontology (though it doesn’t continue in it) and its texts are Sanskrit, it would be better to describe it as a Mahayana school.

Yogachara

Yogachara Buddhism also begins from the Idealistic viewpoint. It takes the position that the only entity whose existence can be affirmed without question is the ‘I’, our consciousness. We know that our consciousness exists, we do not need any further proof of this. Beyond this, the reality of the world cannot be proved and it may be nothing more than a dream.
Yogachara then declares that the world is like a dream only and our consciousness is the only Reality. The phenomena of the world that we see around us do not exist in reality and are things that we dream of. They are compared to the clouds that float across the sky, for the moment they may cover the sky but the sky always remains eternally blue beyond them.
The goal of spirituality is to recognize this, and then through meditation strike down these clouds. We can then exist in our own reality, our own limitless identity, and thus achieve liberation. This is the Nirvana of Yogachara.
Zen is an important school of Yogachara which developed in Japan. Yogachara is also prevalent in China.

Madhyamika

The Madhyamika is the final nihilistic school of Mahayana philosophy.
Madhyamika also starts from Idealistic Ontology. But it denies, not just the world, but the subject as well. Madhyamika says that the world is but a dream. It also says that our consciousness, our subject, is governed and exists only because of this dream. We cannot find any consciousness apart from our thoughts and sensations. But if our thoughts and sensations have no intrinsic reality, being a part of our dream, this means that our consciousness also has no intrinsic reality.
Hence Madhyamika teaches this nihilistic position, that nothing exists in the world and the only existence is Sunyata, or nothingness. This is the essential reality of the world and all others is false.
Nirvana consists of the state of realizing this truth; upon achieving this realization we attain liberation from the ties of this world.

All these schools of Buddhism follow from the original teachings of Gautama Buddha. They all owe allegiance to him. None of the schools can be said to be a higher or lower teaching. They all show different paths to the same state of realization. Each aspirant must choose the path that most appeals to him or her. Since people have different temperaments, each of these paths are necessary as they all attract their own adherents who believe in them and find in them the answer to their spiritual quest.END=NAM MO SAKYAMUNI BUDDHA.( 3 TIMES ).WORLD VIETNAMESE BUDDHIST ORDER=VIETNAMESE BUDDHIST NUN=GOLDEN LOTUS MONASTERY=THE EIGHTFOLD PATH.THICH CHAN TANH.THE MIND OF ENLIGHTMENT.AUSTRALIA,SYDNEY.7/1/2015.