The Apostles Creed takes up the early teachings of the Christian Church in a statement of beliefs:
I believe in the Holy Spirit,
the holy catholic Church,
the communion of saints,
the forgiveness of sins,
the resurrection of the body,
and the life everlasting.
Christians believe their sins are forgiven if they truly repent of their sins, and turn a new leaf.
Some Christian churches have a sacrament of reconciliation, where sins are confessed, and a ritual forgiveness of sins is given.
Forgiveness is personal. One must forgive another's sins as many times as they are done against us, not seven times, but seventy-seven times (an infinite number) as Jesus taught Peter. The kernel of Christian faith is love, and love forgives and forgets.