Salvation typically refers to the process of being saved from an eternal hell, though the details of the concept and the requirements for salvation depend on the religious context in which the term is used. Not all religions include a hell to be rescued from, a heaven to be rescued to or even an eternal soul which requires rescuing.
According to Genesis, Adam and Eve eat of the tree of knowledge and were expelled from the garden of evil. From that time, people committed sins. Everyone born after is affected by this original sin and inherits the guilt of what was done. Salvation is thought of a way to atone for this error. Skeptics dismiss all this as fiction.
Christian views on Salvation
The Roman Catholic church defines two sorts of sins; mortal and venial. The process of salvation relies on the individual's acceptance of God's grace and is sanctified by good works. Any individual who dies with an unforgiven mortal sin (which range from murder to missing mass or other sacraments without a good reason) will spend eternity in hell. Any individual who dies with an unforgiven venial sin (white lies and other minor sins) will go to a temporary hell (purgatory) until those sins have been paid for. Catholics habitually confess their sins to priests who forgive them and prescribe some sort of penance.
The Roman Catholic Church has also offered indulgences, though these are less popular today than in the past. By performing a particularly good task one could be guaranteed salvation. Indulgences were also used to raise money as one could pay to have loved ones released from purgatory, or even pay in advance to have one's own time in purgatory reduced. Roman Catholics can still pay for a priest to say mass on behalf os a diseased loved one and it is hoped these masses ease a soul through purgatory.
Protestantism covers a diverse group with varying doctrines on all issues of Christianity, including salvation. Typically, Protestants believe in salvation by the faithful acceptance of the death and resurrection of Jesus (as an atonement for all sin). Good works are typically considered to be a testimony that this conversion from "sinful" to "saved" (popularly referred to as being "born again") has taken place and do not, on their own, guarantee salvation.
Some believe that salvation is predestined to a select few, others believe salvation is available to anyone. Rituals like baptism are requirements for salvation in some denominations while others hold baptism as an optional rite.
Some Protestants believe that every sin however small deserves Hell and they live in perpetual fear that they will end up in Hell over some minor sins while their church controls them through this fear. Other Protestants believe that once they've accepted Jesus they're saved and seem to believe that they're assured of Heaven but they have to live good lives as well. It gets confusing and it's not clear what they think happens over sins committed after they're saved, after all nobody can stop sinning.
Limited atonement, commonly accepted in Reformed denominations and Calvinism, states that Jesus died to atone for the sins of the whole world (presumably including future sins). However, only the elect are destined by God to receive salvation and to go to heaven. The rest are destined go to hell, which raises the problem of hell. This contrasts with most other denominations of Christianity that claims that everyone has the potential to find salvation depending on either their beliefs or actions.
Orthodox theology considers everyone having the potential and free choice to find salvation, baptism is required, salvation is only found within the church, it is a process requiring sustained effort and not a single action and the search for salvation is equivalent to seeking for communion with God.  There is no assurance of salvation.
Once saved always saved
Some believers claim that they know they have salvation and salvation cannot be lost:
- "The Bible indicates that the blood of Jesus cleanses us from all sin. This means that no sin a believer commits can result in condemnation or loss of salvation. "
However, Adam and Eve were expelled from Eden, which would indicate it is possible to become "fallen" from a non-fallen state. Also, it is difficult to have assurance based on a document as questionable as the Bible. Being saved does not give immunity for the other instructions in the New Testament:
"Whoever says, “I know him,” but does not do what he [Jesus] commands is a liar, and the truth is not in that person."
Faith, works or both?
There is some disagreement in the early and modern church regarding what exactly salvation requires: 
- faith alone (sola fide), emphasised by the epistles and Martin Luther e.g. Galatians 2:16 ,
- faith and works, preferred by most apologists  and the Catholic stance, James 2:24
- faith or works, subject of the Pelagianism heresy,
- works alone, Romans 2:6 , 2 Corinthians 5:10 . Possibly allowed for non-Christians, 
- something else entirely.  
Salvation by works, possibly by works alone, is supported in the apocrypha (non-canonical scripture) and may have been excluded from biblical canon partly because of it:
- Ecclesiasticus 3:30, "Water will quench a flaming fire, and alms maketh atonement for sin."
- Tobit 12:8-9, 17, "It is better to give alms than to lay up gold; for alms doth deliver from death, and shall purge away all sin."
Some denominations claim that a Christian can know they have found salvation. Others believe this is not possible for Christians to know in advance.
Other religious views
Jews reject the idea of original sin and with it the idea that salvation is required. The concept of an afterlife exists within Rabbinic Judaism and is available to all Jews as well as righteous non-jews (those who adhere to the Noahide laws). While the specifics about an afterlife vary among Orthodox, Conservative and Reform Jews, the Christian ideas of salvation, heaven and hell don't have clear analogies in Judaism.
Muslims believe that each person's deeds, beginning at puberty, are recorded and that on Judgment day those deeds will be considered, by God, in order to determine that individual's fate. Faith and God's mercy are also considered and Hell is temporary for those who had faith. The majority of Muslims believe that only Islam offers a path to Heaven. 
Hinduism's concept of salvation is a form of enlightenment or personal realization which breaks the cycle of death and rebirth. The final, ultimate "truth" of the nature of each individual is different.
Buddhists seek an enlightenment (Nirvana), similar to Hinduism, by following the Eightfold path which includes moral behavior and meditation. However, many misconceptions exist around the term "enlightenment". Enlightenment, in its most basic meaning as defined by the Buddha, simply means "seeing clearly", "seeing the things as they are". Enlightened beings still live on this earth, but they can clearly see and understand their way of thinking, and the way they react to things.
The concepts of heaven, hell and even a supreme being do exist in some schools of Buddhism, most notably Tibetan Buddhism with its dozens of spirits, demons and gods. Other Buddhist schools, for example Zen, have done away with any notion of an afterlife, as these claims are not verifiable. Original Buddhism, as taught by Gautama Buddha, encourages practitioners to be skeptical. Venerable Thich Nhat Hanh, a Vietnamese Zen master, says "Do not be idolatrous about or bound to any doctrine, theory, or ideology, even Buddhist ones. Buddhist systems of thought are guiding means; they are not absolute truth."
Generally, atheists do not believe in hell or sin, often because of the lack of evidence for their existence. Therefore, there there is nothing to be saved from and salvation is a meaningless concept. Since the fall did not occur, there is no original sin and no requirement for salvation. Also, it is unclear how guilt can be inherited across generations.
People who leave Christianity are sometimes accused of "never being a true Christian". This is an attempt to avoid the implication that one can lose one's salvation, which is supposedly eternal.
Since someone who has committed many repugnant actions can still have salvation, this seems as incompatible with the idea of a just God. It is also incompatible with the argument from justice, which claims that our actions are rewarded or punished, either in this life or in the afterlife.
Salvation precludes a meaningful relationship with God
A God who threatens heaven or hell based on acceptance of dogma basically does not have a healthy relationship with humans. The threats and incentives would just gather humans that lived in fear or wanted to gain a reward from God - rather like the calculated self interest of Pascal's wager. A superior relationship would be one based on respect, not force.
- "A perfect god would understand that a meaningful relationship is impossible with the constant threat of a dire ultimatum. An ancient barbaric culture, however, would have no such qualms. "
- ↑ Deacon Victor E. Klimenko, The Orthodox Teaching on Personal Salvation, 12/05/2011
- ↑ 
- ↑ Skeptic's Annotated Bible, Is Salvation by faith alone? 
- ↑ Sal Ciresi, Bible says faith and works needed for salvation 
- ↑ Zenit, Nonbelievers Too Can Be Saved, Says Pope, November 30, 2005
- ↑ 194 ways to get saved, Skeptic's Annotated bible
- ↑ 208 ways to get yourself saved, Dwindling in unbelief
- ↑ Pew, The World’s Muslims: Religion, Politics and Society, 2013
- ↑ DarkMatter2525, God's Worst Idea, 20 Mar 2015