Hindus believe in samsara, an eternal cycle of birth, life and deaths or reincarnation, explains How Stuff Works. In Hinduism, each individual soul is considered immortal or eternal. Samsara is controlled by karma, which, in Hinduism, is the moral law of action and reaction. All Hindus believe that each individual accumulates karma during his lifetime and the present condition of the human body and soul is affected by past actions.
Reincarnation means "reenter the flesh." In Hinduism, the soul never dies and just inhabits one body after another during its evolutionary journey. Sometimes, the soul is born into another human body, sometimes in a plant's body, or sometimes an animal body. If an individual accumulates good karma during his lifetime, he may earn a higher place in the Hindu's caste system. If he does evil deeds, his soul may be pushed down to the lowest level of the chain. A person may change his karma by practicing good deeds, yoga or spiritual discipline.
While souls are considered eternal in Hinduism, every Hindus' ultimate goal is to exit the cycle of birth or salvation from samsara, also called moksha. To achieve moksha, a Hindu is expected to break ties from all that binds him to this world and to completely surrender to the Lord. A Hindu who has achieved moksha is released from samsara, which is also seen as an eternal cycle of suffering and pain.