Two knights beside their king hold against a queen: they protect each other's squares and the king, and the queen cannot fork protected pieces. The defender must never let a knight wander.
Two knights are the most drawish pair against the queen. Here the knights on d4 and e4 stand next to the king on e5, and together they cover a large block of squares; the queen cannot win a knight with check because every knight is protected by the king, and the queen cannot approach without walking into a knight fork of her own.