Buddha: a Sanskrit word used in two senses: 1) ultimate Truth or absolute Mind, and 2) one awakened or enlightened to the true nature of existence. The Buddha refers to a historical person with the given name of Siddhartha and family name of Gautama who was born around the year 563 B.C., the son of the ruler of the Shakyas, whose small kingdom lay at the foothills of present-day Nepal. In time he came to be known as Shakyamuni ("the silent sage" - i.e., muni- "of the Shakya clan"). It is recorded that he was married at the age of sixteen and had a son, later to become his disciple. Deeply troubled by the sorrows and tribulations of human life and perplexed by the meaning of birth-and-death, the future Buddha at the age of twenty-nine could no longer live the life of ease and luxury into which he had been born, and he fled his father's palace to become a recluse, a seeker after truth in the solitude of forests. For a time he undertook the severest acetic practices to gain enlightenment. Close to death as a result of these austerities, he at last saw the futility of self-mortification, abandoned it, and finally won perfect enlightenment, becoming "the Buddha." Thereafter for forty-five years, until his death at the age of eighty, he not only taught his own band of monk-disciples but tirelessly trudged the roads of India preaching to all who would listen, always suiting his exposition to the capacity of his hearer's understanding. Men were moved to follow his Way to spiritual emancipation as much by his serenity and compassion as by the wisdom of his words. Eventually his sermons and dialogues were recorded and these sutras (or scriptures) now comprise the basic doctrines of Buddhism.
The Zen sect, in common with other Buddhist sects, accepts the historic Buddha neither as a Supreme Deity nor as a savior who rescues men by taking upon himself the burden of their sins. Rather, it venerates him as a fully awakened, fully perfected human being who attained liberation of body and mind through his own human efforts and not by the grace of any supernatural being. Nor does Buddhism look upon Shakyamuni as the only true Buddha. Just as in previous world epochs, other sages had trodden the same path, attained the same level of perfection, and preached the same Dharma, so would there be Buddhas in subsequent world cycles to lead men to liberation. The historic Buddha, in other words, is but a link in a chain of Buddhas extending from the remotest past to the immeasurable future.
The familiar statement of the Zen masters that we are all Buddhas from the very first must be understood in the sense that potentially everyone is a Buddha, that is, inherently endowed with the unblemished Buddha-nature, but that the candidate for Buddhahood must follow the arduous road to enlightenment if he would realize his innate Perfection. Anyone who has experienced his Buddha-nature, however faintly, has realized the first stage of Buddhahood, since in substance this realization is no different from the Buddha Shakyamuni's. However, in the degree of his enlightenment as well as in the perfection of his character and personality - that is, in his equanimity, compassion, and wisdom-Shakyamuni Buddha towers above the man of average enlightenment. A simple comparison would be between a kindergarten teacher and a university professor; both are instructors, but in their respective levels of attainment there is a vast difference.
Various classifications of the stages of Buddhahood are to be found in the sutras. A Buddha in the highest stage is not only fully enlightened but a "Perfect One, one who has become whole, complete in himself, i.e., one in whom all spiritual and psychic faculties have come to perfection, to maturity, to a state of perfect harmony, and whose consciousness encompasses the infinity of the universe. Such a one cannot be identified any more with the limitations of his individual personality, his individual character and existence; of him it is rightly said that 'there is nothing by which he could be measured, there are no words to describe him.' "
A common statement in some eastern spiritual schools is: "There is no God." This does not mean that they don't believe in God. What they mean is that there is no God that is APART or SEPARATE from your own inner nature. Did not Jesus teach the same thing when he said THE KINGDOM OF GOD IS WITHIN YOU? (Luke 17:21)