Original characters are fictitious, totally fabricated roleplay characters, which are not necessarily connected to certain roleplay fandoms and mostly are fandom flexible/ multiverse. Their background stories are self-invented and the choice of the FC lays in the hands of the writer as well.
canon characters (CCs)
Canon characters are already invented characters from certain fandoms, which are mostly connected to TV series, movies, games, etc. Such characters are being copied by a writer, who portrays the character(s) in his or her own way, possibly in an alternative universe (AU) with fandom flexibility, etc.
the space for creativity in portraying a character is endless