What is Forgiveness?
Forgiveness can best be described as the combination of a full pardon (a guilty person being relieved of the sentence for his crime) and ultimate forgetfulness (no record kept of the crime).
God bestows his forgiveness as a blanket, covering every sin at the same time.
Forgiveness is best described as a commuted sentence for time served. You must first complete the many steps of repentance proving you have earned forgiveness. Then you receive a pardon for the full sentence of eternal death. But a record is kept so that if you commit that crime again your forgiveness is revoked.
Forgiveness is earned from God on a sin-by-sin basis. Mormons will say that forgiveness has been obtained for some of their sins while for others it has not.
It is a significant witnessing opportunity to explain that Christians are fully forgiven and therefore guiltless while Mormons still carry the guilt for most of their sins.