Jesus died in order to pay for our sins, and not only for ours but the sins of the whole world. Jesus' death pays the penalty for sin, and the penalty for sin is death. Because Jesus is divine and infinite in his being, he is able to satisfy the wrath of God against sin in his own body. Having satisfied the penalty for sin through death, death no longer has any hold on Jesus. Since death does not have any power over Jesus, Jesus is raised from the dead. His resurrection is a vindication that Jesus was an innocent man, and that his payment for the penalty for sin is final and complete. When human beings believe in Jesus, they are united to him by faith. This union results in eternal life, since Jesus has eternal life in himself, and has the right to grant it to those who believe in him.
(see Romans 6, 1 Corinthians 15 and Hebrews 10).