This is only the most recent of instances.
If I move my bishop to safety, I lose a knight, but if I do this, I trade a bishop for a pawn, which isn't the best trade, but is better than losing my knight with no compensation.
I assume the previous move was d5. If you moved the bishop to d3 it would capture pawn; you would have the bishop instead of the knight in that variation.
This is only the most recent of instances.
If I move my bishop to safety, I lose a knight, but if I do this, I trade a bishop for a pawn, which isn't the best trade, but is better than losing my knight with no compensation.