The history of Buddhism begins with Siddhartha Gautama, the man who we know as the Buddha, who lived over 25 centuries ago in India. Born as a prince to a privileged family, he abandoned his wealth at a young age to seek ultimate truth and purity of mind. At 35, after years of intense self-discipline, he achieved full enlightenment. He spent the next 45 years, until his death at the age of 80, teaching others the path to peace of mind that he had discovered.
Since that time, the history of Buddhism has diversified into many different paths, the three main traditions being Theravada, Mahayana, and Vajrayana Buddhism. The primary teachings that remain common to all Buddhist traditions are the concepts of anicca, anatta, and dukkha, or impermanence, selflessness, and suffering. In brief, Buddhism teaches that the individual self, the ego, is an illusion of the mind, and that our sufferings result from a belief in that self, and from a dissatisfaction with the world as we perceive it. Believing in the separate self, we constantly seek to fulfill its desires, which are limitless and ultimately insatiable, and thus we end up unhappy.

The path to enlightenment involves a realization and total acceptance of the illusory nature of the self. The primary difference between the three main traditions mentioned above is the existence of the bodhisattva within the latter two. While Theravada Buddhism focuses largely on a rejection of worldly existence and a personal realization of emptiness, both Mahayana and Vajrayana Buddhism teach the Bodhisattva Way, which encourages an enlightened being to remain in the world to help others who wish to reach the same state. Vajrayana differs from Mahayana Buddhism in its use of Tantric methods, which purport to offer a greatly accelerated path to enlightenment within a single lifetime.
Theravada Buddhism is currently widespread in Southeast Asia, including Indonesia, Thailand, Vietnam, and Burma, while Mahayana Buddhism is dominant in Tibet, Nepal, and Mongolia (Tibetan Buddhism), in China (Ch'an), and in Japan (Zen). Beginning in the early twentieth century, all forms of Buddhism have also made great inroads into the West, and Buddhist meditation centers of all traditions can now be found throughout Europe and North America.
This brief glimpse at the 25 century long history of Buddhism is only the slightest taste of a vast body of knowledge that cannot be fully grasped even in an entire lifetime.