Buddhism is a group of various traditions that follow the Dharma ( teaching of the Buddha and wise beings). It involves rituals, meditations, contemplations and guidelines ( such as the eight-fold path) in order to either achieve enlightenment or to work towards the betterment of all conscious beings. The Buddhist Dharma is not a closed cannon. In other words, it applies to material within and outside of sacred texts(Buddhist sutras). Buddhist cannon can included any teaching that helps establish mindfulness or that are geared towards the betterment of humankind. Therefore, the cannon includes Buddhist teachings to books on science, psychology,environmentalism from ancient times to current popular works.
Buddhist teachings and schools are often broken down into three categories: Hīnayāna, Mahāyāna and Vijñāna. Hīnayāna is sometimes considered a disparaging term as it literally means lower wheel. These categories are created mainly by Mahāyāna and Vijñāna schools.
However, it is best to think of Buddhist teachings or schools of thought as a Wheel with first teaching ( first turning of the wheel), the second and the third. The teachings are a circular as opposed to hierarchical and each serve as an aid to the other teachings.
Buddhism is also a karmic religion. Understanding karma is considered to be a a lifetime task or even lifetimes. But this simplest definition is cause and effect ( though I was taught that karma is cause and effect is the results of karma.). Therefore, Buddhism is a karmic religion because it analysis how causes, conditions, consequences, thoughts, actions and emotions effect our daily lives, our minds and our next lives. It poses that karma determines how we view the world, and act within in and it determines the path of our next life.
Reincarnation is an important aspect of Buddhist thought. Each Buddhist sees reincarnation in different ways. Some view it as the constant death and rebirths in one’s current life and might not believe in an actual next life. But the traditional view is that fueled by karma, each person reincarnates in different realms of existence until they reach enlightenment or Buddhahood. However, enlightenment beings are no longer controlled by karma and do not have reincarnate. Unless they have vowed to do so ( such as the reincarnations of Dalai Lama or Karmapa)
General speaking the purpose of Buddhism is either to achieve self-enlightenment or to help all beings achieve enlightenment. Therefore, Buddhas, Bodhisattvas and wise teachers have developed tools from Buddhist debate to meditation in order to aid humans in free oneself of conflicted, unmindful and harmful patterns. They can see enlightenment as being uncluttered emptiness that allows us to see ourselves or the world as it truly is.