Originally, we were created by God to fellowship with Him and enjoy His presence. Unfortunately, we chose to rebel against God's loving and gracious rule. This plunged every human being into a hopeless and godless existence which led to an eternity separated from God in hell. Though God is a loving God, He is also a just God. Sin must be punished.
Sin exacts a penalty and that penalty is death.
This is not just talking about physical death. But, just as God is just He is also loving. His justice demands that our sin is punished, but His love provided someone to take that punishment for us in our place. This means that Jesus died on the cross for you, paying for your sins. He paid the penalty of your sin in your place so you can have an eternal relationship with God.