It's the idea that Humans like to have something to live for, to have a purpose for their being here. Long ago, a couple men wrote books, and these books passed on as truths, creating something called "faith." A very specific faith was brought around about two thousand and thirteen years ago, with the death of a fellow who had led a admirable and dutiful life. After his death, many followers of his preachings felt compelled to share what they knew with the world, and so they wrote a couple more books, put them all together and called it The Bible. At this point, science had nothing. So it was easier to believe a book written and trusted by thousands, especially if your parents believed in it, than saying there is nothing after life. After a lot of wars and killing, we get to today, and the general idea is that you go to church, and you live your life in a specific manner, you get to go to heaven when you die. As for the possibility of there being a God, no one really knows for sure. Well, at least they objectively "can't" know for sure.