Canon is a term that describes a character or storyline that is an original creation of the author or screenwriter. Although it could apply to any original character, for RP and fanfic purposes, canon refers to those characters, relationships, settings and stories that are part of the “official” version of the universe as depicted in the books, TV series or films that inspire the fandom. Canon characters are easily recognized by fans, however, they can and do develop storylines separate from the works which inspired them. Most play or write from within the fandom they created although some also play in the multiverse.
Canon does not imply endorsement or affiliation with the author or creator of the official works or the actors who portrayed the character.