Why does the profit reaches its maximum value at the equilibrium point? 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?
The point where MB = MC is the largest Net Benefit available for a given product.  Therefore, any additional benefit has a lower level of benefit than at equilibrium, and the costs increase at a higher rate than at equilibrium.  In the context of supply and demand, this is where the two lines cross.  But if you think about it in terms of diminishing marginal benefit, and increasing marginal costs then you can see why it is beneficial to product where the largest net benefit occurs.

The following graph is from Markets and the Environment by Keohane and Olmstead and deals with abatement costs, but it is the one graph I think about when someone asks this sort of question because it provides a good example.

As you can see from the graph, the largest net benefit is the furthest distance between the benefit and cost curves.  If you were to take the derivative of each of these functions, you would get linear supply and demand lines, where the largest net benefit is the cross section of the lines (as you can see in the graph below).