A character is a person who exists in a story. Characters may be based on real people (e.g. Napoleon Bonaparte in the Temeraire series), or they may only exist in the book, movie, or game.
Regardless, if the character is indigenous to the story—that is, if they are a canon character—the PPC is sworn to protect their integrity as part of the canon, even if they are a Canon Sue.
If a character is original to the writer but not to the canon, it is an original character, and can be a Mary Sue or Gary Stu. These will be taken care of by the PPC.
There is a third category, the fan character, who is not original to the canon or the writer, but might be used throughout the fandom or by several people for the canon.[source, please!]