The distinguishing characteristics of Zoroastrianism are that it is a religion that believes implicitly in a cosmic struggle between good and evil. Truth and order is pitted against falsehood and disorder, and this conflict is one that includes all of creation, and especially humans, who have an important part to play in this struggle. The religious practices of this religion therefore are based around the need of focusing on good thoughts and committing good deeds and saying good things in order to help the triumph of truth and order.
There are many similarities between Zoroastrianism and other major world religions, such as its belief in an End Times and the final triumph of the forces of good, but what distinguishes Zoroastrianism is its belief in various rituals and practices such as a variety of foods that can and can't be eaten. In addition, when a person is born, they retain a link with their fravashi, or eternal beings that act as guardian angels through a person's life.
Like Christianity, Judaism, and Islam, Zoroastrianism is a revealed religion based on the teachings of prophets, most importantly the prophet Zoroaster. It was a precursor to Islam and is still practiced today, mostly in India and Iran.
Zoroastrianism teaches that Ahura Mazdā, the "uncreated God," is the highest being in the universe, and the greatest of the three Ahura-prefixed Gods. Unlike the three major religions in the world, Zoroastrianism rejects the idea of monasticism, instead allowing all "good" pursuits as being in the service of Ahura Mazdā, and celebrating the joys of worldly pursuits as part of God's order.
Zoroastrianism also contains an apocalypse, Messiah, and resurrection prophecy, although the resurrection will be as a part of Ahura Mazdā instead of as individuals in heaven. A great part of the religion is the role between order and chaos; Ahura Mazdā is the embodiment of order, while Angra Mainyu is the embodiment of chaos; at the End Times, order will triumph.
Like Judaism and Islam, Zoroastrianism contains traditional dietary restrictions on eating animals that are part of chaos (e.g. birds of prey). Unlike Christianity and Islam, Zoroastrianism contains no mission to convert unbelievers, and unlike all three, Zoroastrianism has no religious restriction on intermarriage.