SIN
First, We must have a clear understanding of what sin is....
Transgression of divine law: the sin of Adam. Any act regarded as such a transgression, especially a willful or deliberate violation of some religious or moral principle. Any reprehensible or regrettable action, behavior, lapse, etc.; great fault or offense: It's a sin to waste time. Verb (used without object) to commit a sinful act. To offend against a principle, standard, etc.
The Greek word translated "sin" in the Bible is an interesting term. It, (hamartano), literally means, "to miss the mark." Think of it in this way. In shooting an arrow from a bow, if your arrow flies beyond the target or falls short of it, if it veers to the right of the target or to the left, you "miss the mark." If in our lives we go beyond the will of God, doing things God has said not to do; if we fall short of the will of God by not doing things commanded by God; if we veer away from God's will, doing things for which we have no authority; we "miss the mark" or SIN.
1 John 3:4, "Whoever commits sin also commits lawlessness, and sin is lawlessness." Sin is lawlessness. God has revealed to us His law or will. The Bible is the final authority on sin and its consequences.
The Lord has declared that "no unclean thing can inherit the kingdom of heaven". Our sins make us unclean—unworthy to return and dwell in the presence of our Heavenly Father. They also bring anguish to our soul in this life.
Perhaps the most important fact about sin is its universality. Paul stated in Romans 3:23, "For all have sinned and fall short of the glory of God." In effect, all of us are guilty, and as such face eternal separation from God. All who sin are worthy of death. Because God loves each of us so much, and does not want any to perish, he made the ultimate sacrifice. He sent His Son to die in our place. "For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life" (John 3:16). Because God is just, the penalty for sin had to be paid. Because He cares for us, he sent His Son to pay that ultimate price. "For He made Him who knew no sin {to be} sin for us, that we might become the righteousness of God in Him" (2 Corinthians 5:21). Jesus is our cure for sin.
Sorrow for Sin. In order to be forgiven, we must first acknowledge within ourselves that we have sinned. If we are striving to live the gospel, such an acknowledgment will lead to "godly sorrow," which "worketh repentance to salvation" (2 Corinthians 7:10). Godly sorrow does not come because of the natural consequences of sin or because of a fear of punishment; rather, it comes from the knowledge that we have, through our actions, displeased our Heavenly Father and our Savior. When we experience godly sorrow, we have a sincere desire for change and a willingness to submit to every requirement for forgiveness.
Now, if you understand Sin then let's move on to the second part which is...