What is forgiveness, and does it require reconciliation?
No — and separating the two is the most useful distinction in the subject, because conflating them keeps people in situations they should leave and prevents others from putting down something they are ready to release.
The distinction:
Forgiveness is an internal change — releasing resentment and the desire for retribution toward someone who wronged you. It requires nothing from them, and can occur without contact, without apology, and after their death.
Reconciliation is a relational change — restoring a relationship. It requires both people, and reasonably requires that the behaviour has stopped.
You can forgive without reconciling. You can also reconcile without forgiving, which is more common than acknowledged and tends not to hold.
What forgiveness is not:
Not condoning. It does not make the act acceptable.
Not forgetting, and a demand to "move on" is not forgiveness.
Not a favour to the other person, which is why it can be done unilaterally.
Not obligatory. There is no duty to forgive, and pressure to do so — particularly toward victims of serious harm — is itself a harm, frequently applied by people uncomfortable with someone else's anger.
What the research finds. Forgiveness is associated with lower anxiety and depression, better cardiovascular measures and higher life satisfaction. The direction of causation is not fully settled, and intervention studies suggest genuine effects rather than only correlation. The benefits accrue substantially to the forgiver.
What it actually involves, in the models used clinically: acknowledging the harm fully rather than minimising it; allowing the anger rather than suppressing it; deciding to release the demand for retribution; and reframing without excusing. Skipping the first two produces "cheap forgiveness", which does not last and is associated with worse outcomes.
Self-forgiveness is harder for many people and follows a different path, requiring genuine repair where possible.
When reconciliation is unwise: where harm is ongoing, where there is no acknowledgement, where safety is at issue, or where the relationship was itself the problem. Forgiveness can be complete and the door still closed.