First, what is sin. The typical neo-evangelical definition is anything you think, say, or do that is displeasing to God. That's a nice definition. It covers it, but Biblically, sin is "missing the mark". What is the mark? Many people use the analogy of a bull's eye but I'm not sure that's accurate historically, although helpful. The goal, or mark, is absolute perfection in every area. Any time you come short of that it is sin. This includes error in judgement and thought.
How can anyone meet that standard? It seems hopeless. Well, it is. I'm sure you know that you have not met tat standard. And if you tried really hard from this moment on and gave it all your effort and never sinned again, you'd still fail because you sinned in the past.
So what now? What happens because you sinned?
Well, there is the shame and humiliation of the sins you commit and the consequence those sins have on your loved ones. This is the personal consequence.
Then there are general consequences, which effect all humanity for all sin. One general consequence is aging and decay. We get old, get diseases, then we die. Yippee. When we die, our good deeds are weighed against our bad, and since our bad are infinitely offensive to God, our good deeds are counted as rubbish. The verdict is the same for everyone, we are guilty and condemned and must be punished... eternally.