Well kiddo, God is like a big boss who wants everyone to follow his rules. He says that we should all love and help each other, and not do naughty things like lying or hurting others. But sometimes people don't listen to God and they do bad things, like stealing or hurting someone else.
When someone does something really bad and doesn't say sorry to God or try to make up for it, that's called sin. Now, God is a fair boss and he doesn't want anyone to get away with doing bad things all the time. So, he made a rule that says if you sin a lot and don't try to make up for it, you won't be able to go to heaven and be with him forever.
That's called damnation, which means going to a place where you'll be alone and sad forever, because you didn't follow God's rules. It's not a fun place to be, but it's what happens when someone chooses to keep doing bad things instead of being good.
So, in summary, God is fair and wants everyone to follow his rules. When people choose to sin and not say sorry, they can't go to heaven and they'll have to go to a place where they're alone and sad forever. It's like a punishment for not being good.