The power, usually held by a head of state, to free and/or absolve a person convicted of a crime. Distinct from appeals, which are processed judicially. Questions here should focus on political aspects rather than legal.
The pardon power allows a head of state or other executive to grant clemency to a convict. This can simply be a commutation of the remaining sentence or a full absolution of guilt. As a general rule, nations include rules about how pardons can be granted in their constitutions or other controlling law. Such rules differ for each nation, although they may respect common precedent.