Here is a website if you want to reference scripture but don't have a Bible where you are.
So the basic idea is put forward in Genesis 2 and 3: that the divide between God and people was caused by Adam and Eve eating from the tree of knowledge, which they were told directly not to do by God.
After they eat the fruit, Adam, Eve, the serpent, and the earth all are cursed, and Adam and Eve are sent out of the Garden of Eden.
I was taught (and it makes sense) that there are two different sorts of sin. The first, the more important, is Sin (capital S) which is the essential disconnect between God and people that was caused when Adam and Eve ate the fruit, and in essence, broke their fellowship with God. Since then sin (little s) started to come into the lives of men and women. This is the small petty things, actions, problems, arguments, mistakes, whatnot that plague our lives no matter what we believe, what we do, etc.
The idea is that when Sin is forgiven through Jesus, God allows us to come more and more directly into his presence as we have faith, as we gain the experience of Him, and as we pursue Him. Little s sin never completely goes away because it has become so ingrained into our behavior, our society, and our world. But in the end they are not important as long as the parties involved keep their eyes on God, and continue to desire a relationship with Him.
Sin is obvious to me - a couple years ago I looked around and realized how easy it was for people to screw things up. Incredibly easy. Something as small as picking one word over another can cause a problem, even if your not angry or arguing. Business is obviously flawed; look at what America's business has done to our economy and to the rest of the world. There is disease and disorders in the world. I suppose I have taken the lack of perfection as a proof of Sin, and the fallen state we and the world are currently in.
I'm interested in hearing what other people have to say about this. For instance, why should things in their natural state be perfect and not imperfect? What do you think of the concept of Sin and it's effect on the world around us? I don't think anyone can deny that things are screwed up right now.