I am a Christian. That means that I believe the good news that God sent his son Jesus, who was born as a man, to die on the cross, taking the punishment we deserve for our sins on himself so that we don't have to face them. I believe that he rose again, proving that God was satisfied with the sacrifice he made, so we can have total confidence that if we trust in Jesus' death, we can go to heaven.
That might sound a bit strange, but it's really quite simple - the Bible says that God deserves to be honoured because he created and sustains the universe:
You are worthy, our Lord and God, to receive glory and honour and power, for you created all things, and by your will they were created and have their being.Revelation chapter 4, verse 11
The problem is that we don't do that - we are happy to take all the good things God gives us, but don't want to have anything to do with him. This is what the Bible calls sin.
Sin is the act of removing God (our creator) from his rightful place as head of our lives, and putting ourselves in his place, and we all do it.
The Bible is very clear on what the consequences of Sin are. God must (because he is perfectly just) punish us for those sins:
For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.Romans chapter 6, verse 23
The heart of Christianity is the good news in the second part of that verse - that God gives us the gift of eternal life if we accept Jesus as our Lord.
But how can a perfectly just God just sweep that sin under the carpet - the punishment needs to be paid by someone! That's where Jesus comes in. He lived a perfect life and never sinned, then died on a Roman cross. In dying he took the punishment (death) that we deserve for our sins instead of us, so we don't have to. That means we can have a relationship with God, and receive that gift of eternal life!