Although a real game probably wouldn't look like that. the idea behind it that a piece (the rook) is blocked from causing check. However the piece that's causing the block (the knight) has the chance to move into a normally bad position and utilizes the enemy king's check to make an effective attack
Also this particular move where the king is in check but can easily move away. Unfortunately the same cannot be said for his queen.
Although a real game probably wouldn't look like that. the idea behind it that a piece (the rook) is blocked from causing check. However the piece that's causing the block (the knight) has the chance to move into a normally bad position and utilizes the enemy king's check to make an effective attack
Also this particular move where the king is in check but can easily move away. Unfortunately the same cannot be said for his queen.