Good Friday is the day in which Christians celebrate the crucifixion of Jesus Christ on the Christ that occurred in early A.D. (There's B.C. Before Christ. and A.D. Anno Domini, Latin for “in the year of the Lord").
Christian's believe Jesus Christ to be God's only Son. The only way to be saved from eternal damnation (I did not swear this is the proper context), is to believe in Jesus Christ and accepting Him into your heart. The reason we need this is because of sin. (Sin is a transgression of the law of God,["Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness." 1 John 3:4 ESV] and rebellion against God. ["Whoever rebels against your commandment and disobeys your words, whatever you command him, shall be put to death. Only be strong and courageous.”" Joshua 1:18 ESV]), Everyone has sinned, ("For all have sinned and fall short of the glory of God," Romans 3:23. "as it is written: “None is righteous, no, not one;" Romans 3:10.) and there is nothing we can do to glorify God with our own power. Our best works are like filthy rags. Since all have fallen short of God's glory, and none are righteous, then how can we be saved? Are we forever stuck to suffer in the depths of hell? Well, because God's grace, there is good news. ("For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast." Ephesians 2:8-9 ESV) The Good News is that Jesus Christ died on the cross. It may not seem good that someone died on the cross approximately 2000 years ago, but let me explain. Jesus Christ is the Son of God, who came to earth as a baby. He was born of a virgin, and lived a sinless life. (“And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. He will be great and will be called the Son of the Most High. And the Lord God will give to him the throne of his father David, and he will reign over the house of Jacob forever, and of his kingdom there will be no end.” And Mary said to the angel, “How will this be, since I am a virgin?” And the angel answered her, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy—the Son of God.” Luke 1:30-35 ESV) ("For to this you have been called, because Christ also suffered for you, leaving you an example, so that you might follow in his steps. He committed no sin, neither was deceit found in his mouth." 1 Peter 2:21-22 ESV) So Jesus Christ, the Son of God (the Father), gave his life up on the cross for the sins of the entire world. The day of Good Friday is the day we remember Christ's crucifixion on the cross. ("He is the propitiation for our sins, and not for ours only but also for the sins of the whole world." 1 John 2:2 ESV) Because Christ lived a perfect life, and took on the sins of the world, that is the only way we can be with God forever. (No Heaven is not just a place where humans string harps and sing all day. Someday I'll write an article on that.) Without Jesus Christ, we would be forever be children of wrath, disobeying the Creator of the Heavens, and the Earth and doomed to hell. This is why Jesus said "I am the way, and the truth, and the life. No one comes to the Father except through me." John 14:6. Without this sacrifice, we could never be set free. This is why we celebrate Good Friday, for Christ died on the cross for the sins of the world. God so loved the World that He gave His only Son, so that whoever believes in Him shall not perish but have eternal life. )