Traditional Zoroastrianism does not believe in rebirth (although some modern Parsis do under Hindu influence). Zoroastrians believe that every person is created to fight evil and expand the Good Creation. Humanity was created perfect, immortal, sinless, without need and happy. All misery, suffering, disease and death are afflictions of an independent force of evil (Ahriman). Each individual has free will and so can choose to practice Righteousness (Asha) or follow the path of evil, but will be judged according to their thoughts, words and deeds in this life.
Iranian Zoroastrians and more liberal Parsis stress the rationality and logical nature of the religion, and find support for their views in the Gathas (Hymns of Zoroaster). Traditionally, the religion talks about the creation of the universe and views history as the battle ground between good and evil. It looks forward to the renovation (frashegird or frashokereti), when good will ultimately triumph over evil, when the saviour (Soshyant) will come, the dead will be raised and the final judgment will take place. At this point good will be rewarded and evil punished, before passing into the ideal existence where heaven and earth come together in what is literally, the best of both worlds.
Fundamentally, it is personal identity that is most important to individual Zoroastrians, alongside the link between their race and their religion.