Buddhism is divided into three main branches. The oldest branch is Theravada, the “Way of the Elders.” Theravada is predominately found in southern Asia (Sri Lanka, Burma, Thailand, and Cambodia). By far the largest branch of Buddhism is Mahayana or “Great Vehicle.” It is predominant in northern Asia (China, Japan, Korea, and Vietnam). “Zen Buddhism is a form of Mahayana Buddhism that has become very popular in Western nations in recent years. Zen developed about a thousand years after the death of Buddha. Adherents of Zen say their beliefs do not need to be explained, but are directly transmitted from one mind to another…. A statement of Buddha frequently repeated by advocates of Zen is: ‘Look within; you are the Buddha.’” [9] The third branch of Buddhism is the Vajrayana or “Diamond” tradition. It is dominant in Tibet. The Dalai Lama is the leading figure of this branch.
Though there are different branches of Buddhism, there are some basic teachings accepted by all. These include: The Three Marks of Existence, The Four Noble Truths, The Five Skandhas, The Six Realms, The Eightfold Path, and the Ten Perfections. [10]
“Theravada Buddhism has three groups of scriptures. Together, they are referred
to as ‘Trip taka’ which means ‘Three Baskets.’ The Trip taka is about eleven times the size of the Bible. It includes the sayings of Buddha, lectures on discipline, and philosophy. Mahayana Buddhism has no fixed canon of scripture. They have more than 5,000 volumes and the number continues to grow. Some sects choose one portion to follow; some another.” [11]
Some of the main doctrines of Buddhism are karma, reincarnation, and nirvana.

suggested reading:

The Question, Vol. 1: Zen and Violence