Nearly 2,000 years ago, God sent His only Son, Jesus Christ, to the earth to suffer and die for the sins of humanity. If God hadn't done this, we would all have to be punished for our own sins. The punishment for sin--even just one sin--is death. The Bible states in Romans 6:23 that "the wages of (or punishment for) sin is death..."
Because Jesus Christ suffered and died for your sins and for mine, He now offers each and every one of us a free gift of eternal life. God wants us to accept this free gift, so that when we die, we can leave this earth to go and live in Heaven with Him forever.
John 3:17-18 says, "For God did not send His Son into the world to condemn the world, but that the world through Him might be saved. He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God."