Buddhism is one of the leading world religions in terms of adherents, geographical distribution, and socio-cultural influence. While largely an "Eastern" religion, it is becoming increasingly popular and influential in the Western world as well. It is a unique world religion in its own right though it has much in common with Hinduism in that both can be called "eastern" religions, believing in Karma (cause and effect ethics), Maya (illusory nature of the world), and Samsara (the cycle of reincarnation) among other things. Its founder Siddhartha Guatama was born into royalty in India nearly 600 years before Christ. As the story goes he lived luxuriously growing up and even marrying and having children with little exposure to the outside world. His parents intended for him to be spared from influence by religion and any exposure to pain and suffering. However it was not long before his thin shelter was penetrated and he caught a glimpse of an aged man, a sick man, and a corpse. His fourth vision was of a peaceful ascetic monk (one who denies luxury and comfort). Seeing his peacefulness he decided to become an ascetic himself. He abandoned his life of wealth and affluence to pursue enlightenment through austerity. He was very skilled at this sort of self-mortification and intense meditation. He was a leader among his peers. Eventually he let his efforts culminate in one final gesture. He "indulged" himself with one bowl of rice and then sat beneath a fig tree (also called the Bodhi tree) to meditate till he either reached enlightenment or died trying. Despite his travails and temptations, by the next morning, he had achieved enlightment. Thus he became known as the 'enlightened one' or the 'Buddha.' He took his new realization and began to teach his fellow monks, with whom he had already gained great influence. Five of his peers become the first of his disciples.
What had the Gautama discovered? Enlightenment lay in the "middle way," not in luxurious indulgence or self-mortification. Moreover he discovered what would become known as the ‘Four Noble Truths’ – (1) to live is to suffer (Dukha), 2) suffering is caused by desire (Tanha, or "attachment"), 3) one can eliminate suffering by eliminating all attachments, and 4) this is achieved by following the noble eightfold path. The "eightfold path" consists of having [a] right 1) view, 2) intention, 3) speech, 4) action, 5) livelihood (being a monk), 6) effort (properly direct energies), 7) mindfulness (meditation), and 8) concentration (focus). The Buddha's teachings were collected into the Tripitaka or "three baskets." [Win Corduan, Neighboring Faiths (IVP, 1998): 220-224].
Back of these distinguishing teachings are teachings common to Hinduism, namely Reincarnation, Karma, Maya, and a tendency to understand reality as being Pantheistic in its orientation. Buddhism also offers an elaborate theology of deities and exalted beings. However, like Hinduism, Buddhism can be hard to pin down in regards to its view of God. Some streams of Buddhism could legitimately be called atheistic, while others could be called pantheistic, and still others theistic such as with Pure Land Buddhism. Classical Buddhism however tends to be silent on the knowability or reality of an ultimate being and is therefore considered atheistic.
Buddhism today is quite diverse. It is roughly divisible into the two broad categories of Theravada (small vessel) and Mahayana (large vessel). Theravada is the monastic form which reserves ultimate enlightenment and nirvana for monks while Mahayana Buddhism extends this goal of enlightenment to the laity as well, that is, to non-monks. Under these categories can be found numerous branches including Tendai, Vajrayana, Nichiren, Shingon, Pure Land, Zen, and Ryobu among others. Therefore it is important for outsiders seeking to understand Buddhism that they not presume to know all the details of a particular school of Buddhism when all they have studied is classical historic Buddhism. (Corduan, 230).
It is important to be aware that the Buddha never considered himself to be a god, or a divine being of any type, rather he considered himself to be a ‘way-shower' for others. Only after his death was he exalted to God-like status by some of his followers, though not all of his followers viewed him that way.
Recommended Resource: Jesus Among Other gods by Ravi Zacharias.