Zwingli and Calvin, like most traditional Christians, believed that this life was simply a pilgrimage, a journey toward our final destination. That destination was an eternity spent either in heaven or in hell. There was nothing one could do to earn a spot in heaven-God freely forgave the sins of some, and they could enter heaven. Heaven is a state of blessedness where you exist in the presence of God, something humans have not been able to do since the fall in the Garden of Eden. Hell was a place of torment, as just punishment for sin.
The Reformers rejected the Roman Catholic teaching that there is also a place called purgatory, because purgatory is not explicitly mentioned in the Bible. The belief in purgatory developed over the course of the Middle Ages, driven by the logic of the Catholic system of sanctification. Those who were baptized and thus cleansed of the stain of original sin still had to pay the debt for the offense of sin to a perfect God. (In addition, any additional sins must be paid for.) You earned merits toward the debt by performing works, especially the sacraments. Since no work of a finite fallen being on its own would count for much, only works performed within the structure of God's grace mediated by the Church counted.
Very few people led a life sufficiently sinless and with enough good works to be out of debt when they died. Those who did were saints. Those who had made sufficient but not complete progress on the path of sanctification were sent at death to purgatory, which was exactly like hell (full of torment) to burn away or purge the remaining sin. The difference between purgatory and hell is that there is an end point to purgatory: when your sins are purged you may enter heaven. Luther argued instead that all were sinners, always. Saints were all Christians whose sins had been forgiven.
Reformed Christians traditionally have not believed that it is possible to live a sinless life, even after one is saved and one's sins have been forgiven. Nevertheless, for those who are saved (the "saints," or the "elect") blessedness is possible on this earthly pilgrimage toward heaven. Blessedness consists in the confidence that, despite being a sinner, God has forgiven your sin, and has your best interests at heart. One's proper relationship to God, lost by Adam in the fall, is thereby restored. God is experienced as a benevolent and loving Father; you are relieved of anxiety about your future; you live in the awareness that the point of life is not your own happiness but the Glory of God (in Calvin's colorful phrase, you are a spectator in the theater of God's glory)-ironically this awareness is the key to happiness.
Calvin and Luther agreed that on judgment day, at the end of history, all the dead from throughout human history would be resurrected and would possess some sort of physical body that resembled but was different from the body possessed during their earthly existence. At the final resurrection of the dead, the saints (or, the elect) enter heaven, the damned are sent to hell.
Calvin and Luther disagreed on the state between the time of death and this resurrection and judgment. Luther believed that souls slept until judgment day. Calvin insisted that the dead souls of the saved rested in a blessed state until they were resurrected.
In the past, the major split in Christianity on the afterlife was between Lutherans and Calvinists on the one hand, who argued that humans played no role in their own salvation, and Catholics and Methodists who argued that free will and works played a role. In more recent years, the more significant split has been between the more conservative and more liberal wings of each Protestant denomination.
The conservative wing of the Reformed churches maintains its belief in an afterlife spent in a literal place, either heaven or hell. More liberal Reformed Christians tend to downplay hell, often because the image of God allowing people to suffer eternally, even if they are sinners, is not easy to match up with their idea of a loving God. Some contemporary scholars have reinterpreted the doctrine of predestination in new ways that allow a broader understanding of the work of God's grace.
In recent surveys, far more Americans say that they believe in heaven than say they believe in hell. There are also Reformed Christians who, since the mid- 20th century (this is true of all Protestant denominations), hold that neither heaven nor hell is a literal place. If the core of salvation as described above is to live in the presence of God, heaven is then a metaphor for blessedness or a divine relationship in this life. Hell is a metaphor for living in the absence of God in this life.