When we talk about marginal cost and marginal benefit/cost, why does the equilibrium point is the most convenient for the production of a product. If the marginal cost and the marginal benefit/revenue are the same Wouldn't the cost of producing a product would be the same as the revenue you obtain from selling it? Wouldn't you be earring nothing when you reach the equilibrium point?

Extra question; Are marginal benefit and marginal revenue the same concept?