So ELI5, if you are a little baby sheep and your Shepard was out caring for the flock. He provides a vast world for you to live in but there are bad things in the world and your little sheep brain can fall easily to these bad things. Your Shepard realises there is a way he can show you to live well without him around all the time, but it takes a big sacrifice on his part. He takes a look and goes you know what, I'll be a symbol, I'll give up my Shepard life and hopefully you will see, there is a bigger picture and a greater good. So little sheep, you can live in a bad world where people do bad things and I guess everyone suffers from it. Or you too can be like your Shepard and make sacrifices to be a good sheep, and if enough other sheep do the same the flock will be a pretty good place to be. PS. I'm not Christian but I figure that's the gist of the whole thing