Buddhism is one of the oldest religions on the earth. Like Judaism it's origins are shrouded in oral history and legend. Like Judaism, it's principle stories take place near the beginning of the classical period of history, sometime between 1000 BC and 500 BC, approximately. There is some evidence that Buddhist ideas and the ideas that became Christian and Rabbinic Judaism ideas shared a common "field". That is why many of them are similar at the spiritual "hidden" level. Thee is no question that both influenced each other. This parallelism of origins is further reinforced by the unearthing of gnostic Christian Scriptures which show a clear parrallel in teachings.
Three Important teachings
Buddhism starts with the "Buddha." This Buddha's name was Siddhartha, and he was a prince who renounced the princely life, and according to legend the chance to become a great "wheel turning king" and conquer the world, for the life of a religious person. In doing so he became the founder of Buddhism on Earth. For most Buddhists that makes him the "original Buddha." Not that there aren't other Buddha's, or even claimants to profound teachings, but it is partly an honorific that as the historic Buddha he gets "first place."
Phenomenal Buddha
Mahayana Buddhists make a differential between this historical Buddha and what is known as the "original Buddha" or the source of all Buddhas. The Buddha is also said to be "tripartate" and to have a "Dharma or Law" Body, a Phenomenal Body, and a Bliss Body. The Phenomenal Body can manifest anywhere but is usually located in Shakyamuni Buddha. The idea of Buddhism is that we too can manifest the Phenomenal Body of the Buddha eventually. This is known as "Achieving Buddhahood." In Nichiren Buddhism the implication is that ordinary people can manifest the phenomenal Body in their present existence, usually assumed as a manifestation at the moment of death. However, there are layers of myth and legend which have been added into Buddhism which deify this "Buddha Body" to the point where only a superman could ever manifest it literally. Misunderstanding this notion leads to delusions about what the Buddha nature is and what people can achieve by practicing Buddhism. There is a tendancy of Buddhists to "reify" or personalize the Buddha on the one hand, or to assume that Buddhahood is beyond their reach and reach for a lesser goal, or to equate the Buddha with all the mythological or highly figurative language that has developed about him. In those traits Buddhism is very much like the other major world religions.
Bliss Buddha
This "Buddha" is said to manifest himself to ordinary mortals as a source of "Bliss" and is also known as the "Bliss Buddha." When Joseph Campbell says "follow your bliss" he is in a way advocating following this "Bliss Buddha." The Buddha is said to actually have "three bodies." One is the "literal body" or physical Body, which the "Buddha" in Mahayana teachings can have more than one of. Then there is this "Bliss Buddha" body which is what enables the Buddha to manifest himself in this world even when otherwise not present and which isn't literally a body. And finally he has a "dharmakaya" or "dharma" body.
Law Body
This introduces the next subject. The "dharma." Dharma has a whole host of translations. It is like the Judaic concept of "Torah" which means not just "bible" but also law and teaching. Similarly Dharma is "Law", but "dharma" is also lessons and teachings, truths and wisdom. One follows the "dharma" by following the truth about reality. The "Dharma Kaya" thus is really the "laws" that enable a Buddha to be enlightened by providing the "text" he/she is enlightened to.