A pardon is a legal practice, whereby a criminal's offenses are legally blotted out, or a conviction is erased. Normally this can be issued only by the highest-ranking authorities around — the emperor, the king, the president.
Fictionally the overwhelming use of them is to allow the Lovable Rogue (or, less often, a less charismatic villain) to get off the hook by doing the kingdom a great favor: [...] [tvtropes.org]