Mary-sue- Mary-sue's are 'perfect' characters. Their main features are terrible pasts, being overpowerfull, beautiful and flawless. Read the full article here.
OC- (Original Character) a character that was created from a scratch, usually does not include screeshot edits. Original Characters in most cases have their own stories that might be associated with the main Naruto plot.
RPC- (Roleplaying Character) a character that is usually produced from a screenshot and is included/created in the main Naruto plot.
Screenshot edit- A picture/anime screenshot that has been drawn over/edited in MSPaint or other image edititng software
Canon - main characters in the Naruto story. Sasuke, Naruto and Sakura are great examples.