According to the Trinitarian interpretation of the New Testament, Jesus was both human and God , so he had the power to lay his life down and to take it up again; thus after Jesus died, he came back to life. This event is referred to in Christian terminology as the resurrection of Jesus Christ, and is commemorated and celebrated by most Christians annually on Easter Sunday.
Roman Catholic view of Resurrection: Held by the majority of Christians, the Catholic view is that Jesus willingly sacrificed himself as an act of perfect obedience, atoning for the disobedience of Adam, and thus cleansing Mankind of the stain of original sin. Jesus's sacrifice was an offering of love that pleased God more than man's sin offended God, so now all who believe in Jesus and keep his commandments may receive salvation in his name.
For Christians, the historicity of the resurrection is seen as crucial, as most tend to assume that if Jesus has power over life and death, then he is the Son of God.