Wrong bishop
The wrong bishop is a bishop that does not control the promotion square of a rook pawn, so the defender can draw by sitting in the corner.
An a- or h-pawn promotes on a dark or light square. If your bishop cannot attack that square, you cannot eject a king that reaches the corner. Stalemate ideas appear as soon as the king is boxed in.
The h-pawn promotes on h8, a dark square. The bishop on f1 is light-squared. If Black’s king gets to h8 and stays there, White cannot force it out.
With any other pawn, or with a bishop that matches the promotion square, the ending is usually a win. The word “wrong” is only about that one corner.