Sin is breaking any of God's laws (commands, precepts, judgments, etc.) most of which are stated in The Law, i.e., the first five books of the Bible: Genesis, Exodus, Leviticus, Numbers and Deuteronomy.
When we demonstrate our faith in his son Jesus Christ, God the father forgives us all our past sins and we become perfect and qualify for Eternal Life with Him. demonstrate our faith in his son Jesus Christ.