"What is Buddhism and what do Buddhists believe?"
Answer: 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. With Christianity however, it is stated quite clearly in the bible that Jesus was the Son of God (Matthew: 3  and behold, a voice out of the heavens, saying, 'This is My beloved Son, in whom I am well-pleased) and that He and God are one (John 10:  I and my Father are one). One cannot rightfully consider himself or herself Christian without professing faith in Jesus as God.
Jesus taught that He is the way, and not simply one who showed the way as John 14:6 confirms, "I am the way, the truth, and the life. No one comes to the Father except by me." By the time Guatama died Buddhism had become a major influence in India; three hundred years after his death Buddhism had spread so far that it encompassed most of Asia. The scriptures and sayings attributed to the Buddha were written about four hundred years after his death. This delayed period between his death and the writing or commentary containing his message allows for several scholarly challenges to arise over the authenticity and reliability of Buddhist scriptures.
The Buddha lived and died well before the time of Jesus. His travels never took him more than a couple of hundred kilometers from his home. The bible and its message do not appear to have been known by the Buddha, and in fact he never spoke of God, or Jesus; consequently Buddhists, generally don’t speak out for God as Christians do. In its classical form, Buddhism does not speak of any personal God or Divine Being.
Sin is largely understood to be ignorance. And where it is understood as somehow "moral error" the context in which "evil" and "good" are understood is amoral. Karma is understood as nature's balance and is not personally enforced. Nature isn't moral, therefore karma is not a moral code, therefore sin is not ultimately moral. Thus we can say, by Buddhist thought, that our error is never ultimately moral since it is ultimately just an impersonal mistake and not an interpersonal violation. The consequence of this understanding is devastating. For the Buddhist, sin is more akin to a typo than to transgression against the nature of omnipotent God. This understanding of sin does not accord with the innate moral consciousness that men stand condemned because of their sin before a holy God (Rom. 1-2).
Since sin is impersonal and fixable error, it does not issue in the doctrine of depravity as it does in Christianity. With Christianity, man's sin is a problem of eternal and infinite consequence. Buddhist views of sin do not compare. Therefore there is no need for a Jesus' character to rescue people from their damning sins. For the Christian Jesus is the only means of rescue from eternal damnation over our personal (and imputed) sins. For the Buddhist there is only ethical living and meditative appeals to exalted beings for the hope of perhaps achieving enlightenment and ultimate Nirvana. But more than likely one will have to go through a number of reincarnations to pay off their vast accumulation of karmic debt. For the true followers of Buddhism the religion is a philosophy of morality and ethics, encapsulated within a life of renunciation of the ego-self. One may appeal to countless Boddhisatvas ("Buddhas in the making") or Buddhas (Gautama is later viewed as being one among many Buddhas) (Ibid., 229). But ultimately reality is impersonal and non-relational therefore it is not loving. Not only is God seen as illusory, but in dissolving sin into non-moral error and by rejecting all material reality as maya ("illusion") even we ourselves lose our "selves." Personality itself becomes an illusion.
When asked how the world started, who/what created the universe, the Buddha is said to have kept silent because in Buddhism there is no beginning, and no end, instead there is an endless circle of birth and death. One would have to ask what kind of being created us to live, endure so much pain and suffering, and then die, over and over again? It may cause one to contemplate, what’s the point, why bother? Christians know that God sent His Son to die for us, just the one time, so that we don’t have to suffer for an eternity. He sent His Son to give us the knowledge that we aren’t alone, and that we are loved. Christians know there is more to life than suffering, and dying (2 Timothy: 1 But is now made manifest by the appearing of our Savior Jesus Christ, who hath abolished death, and hath brought life and immortality to light through the gospel).
Buddhism teaches that Nirvana is the highest state of being, a state of pure being. And it is achieved by means relative to the individual. Nirvana defies rational explanation and logical ordering therefore it cannot be taught, only realized. Jesus in contrast was quite specific, He taught us that our physical bodies die but our souls ascend to be with Him in heaven (Mark: 12  for when they shall rise from the dead, they neither marry, nor are given in marriage; but are as the angels which are in heaven). For Buddhists there is no merciful Father in heaven who sent His Son to die for our souls, for our salvation, to provide the way for us to reach His glory. The Buddha taught that people don’t have individual souls for the individual self or ego is an illusion.