A Production Possibility curve is basically a graphical representation that shows various maximum combination of output that a country can produce with limited economic resources in a fixed period of time.
The production Possibility curve slopes downward because, it is showing an increase in the number of units of the product X. Now the graph is showing that more number of unites of X product can be produced only by sacrificing the number of goods of product Y.
Thus a choice must be made between the two products or a combination of the two products.
