There are many substantial and vital distinctions between Judaism and Christianity. Of course there are many similarities, primarily because Christianity emerged from Judaism. However, the emergence was not a direct line. Christianity broke from Judaism, forming a new religion, so it is misleading, however comfortable the thought might be, to believe that the two religions are essentially the same, or to see Christianity as the natural continuation of Judaism.

Judaism's central belief is that the people of all religions are children of God, and therefore equal before God. All people have God's love, mercy, and help. In particular, Judaism does not require that a person convert to Judaism in order to achieve salvation. The only requirement for that, as understood by Jewish people, is to be ethical. While Judaism accepts the worth of all people regardless of religion, it also allows people who are not Jewish but who voluntarily wish to join the Jewish people to do so.

Judaism insists on a notion of monotheism, the idea that there is one God. As Judaism understands this idea, God cannot be made up of parts, even if those parts are mysteriously united. The Christian notion of trinitarianism is that God is made up of God the Father, God the Son, and God the Holy Spirit. Such a view, even if called monotheistic because the three parts are, by divine mystery, only one God, is incompatible with the Jewish view that such a division is not possible. The Jewish revolutionary idea is that God is one. This idea allows for God's unity and uniqueness as a creative force. Thus, for Jewish people, God is the creator of all that we like and all that we don't. There is no evil force with an ability to create equal to God's. Judaism sees Christianity's trinitarianism as a weakening of the idea of God's oneness. Jewish people don't have a set group of beliefs about the nature of God; therefore, there is considerable, and approved, debate within Judaism about God. However, all mainstream Jewish groups reject the idea of God's having three parts. Indeed, many Jewish people see an attempt to divide God as a partial throwback, or compromise with, the pagan conception of many gods.

To Christians, the central tenet of their religion is the belief that Jesus is the Son of God, part of the trinity, the savior of souls who is the messiah. He is God's revelation through flesh. Jesus was, in Christian terms, God incarnate, God in the flesh who came to Earth to absorb the sins of humans and therefore free from sin those who accepted his divinity.

To Jewish people, whatever wonderful teacher and storyteller Jesus may have been, he was just a human, not the son of God (except in the metaphorical sense in which all humans are children of God). In the Jewish view, Jesus cannot save souls; only God can. Jesus did not, in the Jewish view, rise from the dead.

He also did not absorb the sins of people. For Jewish people, sins are removed not by Jesus' atonement but by seeking forgiveness. Jewish people seek forgiveness from God for sins against God and from other people (not just God) for sins against those people. Seeking forgiveness requires a sincere sense of repenting but also seeking directly to redress the wrong done to someone. Sins are partially removed through prayer which replaced animal sacrifice as a way of relieving sins. They are also removed by correcting errors against others.

Jesus, for Christians, replaced Jewish law. For traditional Jewish people, the commandments (mitzvot) and Jewish law (halacha) are still binding.

Jesus is not seen as the messiah. In the Jewish view, the messiah is a human being who will usher in an era of peace. We can tell the messiah by looking at the world and seeing if it is at peace. From the Jewish view, this clearly did not happen when Jesus was on Earth or anytime after his death.

Jewish people vary about what they think of Jesus as a man. Some respect him as an ethical teacher who accepted Jewish law, as someone who didn't even see himself as the messiah, who didn't want to start a new religion at all. Rather, Jesus is seen by these Jewish people as someone who challenged the religious authorities of his day for their practices. In this view, he meant to improve Judaism according to his own understanding not to break with it. Whatever the Jewish response is, one point is crucial. No one who is Jewish, no born Jewish person and no one who converts to Judaism, can believe in Jesus as the literal son of God or as the messiah. For the Jewish people, there is no God but God.

Judaism does not accept the notion of original sin, the idea that people are bad from birth and cannot remove sin by themselves but need an act of grace provided by the sacrificial death of Jesus as atonement for all of humanity's sins. For Christians, there are no other forms of salvation other than through Jesus.

In contrast, the Jewish view is that humans are not born naturally good or naturally bad. They have both a good and a bad inclination in them, but they have the free moral will to choose the good and this free moral will can be more powerful than the evil inclination. Indeed, Jewish ethics require the idea that humans decide for themselves how to act. This is so because temptation, and with it the possibility of sin, allows people to choose good and thus have moral merit. The Jewish view is not that humans are helpless in the face of moral error.

In general, Jewish thinkers have focused on the ways to lead a good life on Earth and improve this world, leaving concerns about death and beyond until the appropriate time. Judaism has stressed the natural fact of death and its role in giving life meaning. Of course, issues of death are inevitably important. The fear of death, concern about the fate of our own soul and those of our loved ones, ethical concerns that some people die unfairly, all these and many other issues are discussed in Jewish literature. Since God is seen as ultimately just, the seeming injustice on Earth has propelled many traditional Jewish thinkers into seeing the afterlife as a way to reflect the ultimate justice of human existence.

Traditional thinkers considered how individuals would be rewarded or punished after their deaths. There are a few rare descriptions of life after death. Traditionalists gave the name Gehenna to the place where souls were punished. Many Jewish thinkers noted that since, essentially, God is filled with mercy and love, punishment is not to be considered to be eternal. There are, similarly, many varying conceptions of paradise, such as that paradise is the place where we finally understand the true concept of God. It is also possible that there is no separate Heaven and Hell, only lesser or greater distance from God after death. In addition, punishment might be self-determined on the basis of suffering in kind the suffering the person brought about. That is, Judaism doesn't have a clear sense of Heaven and Hell, with different places in Hell for different punishments. Rather, the idea is that God uses the afterlife to provide ultimate justice and for the wicked to seek some sort of final redemption.

Judaism does not believe people who are Gentiles will automatically go to Hell or that Jewish people will automatically go to Heaven on their basis of their belonging to the faith. Rather, individual ethical behavior is what is most important. Many traditional Jewish people believe that Judaism provides the best guide to leading such an ethical life.