The curve, said to resemble a duck, is a graphical representation of the gap and imbalance between solar production and peak demand over the course of a day. It shows a dip in net demand during midday when solar generation is typically highest, followed by a rise in the late afternoon and evening as solar generation decreases and demand increases. Managing the curve, especially during weather changes or solar events, is crucial for grid stability and requires efficient energy storage and demand response strategies.