Producer surplus is the price of a good or service, in excess of the marginal cost of producing it, summed over the quantity produced.
Producer surplus is the difference between how much of a good or service the producer is willing to supply versus how much they receive back in trade. The surplus is the benefit that the producer receives from selling the good in the market. Having a surplus is the goal for a producer because they are benefiting by receiving money for the products being purchased by consumers.