The use of objects in non-literal ways. It involves assertions that do not depend on being either true or false, and actions that do not depend upon being in factual accord with reality. You can assert that you are a pretend frog and be safe from being disproved by someone pointing out that you are not really and truly a frog. You can pretend that a jug has lemonade in it, and pretend to pour the non-existent liquid into an empty cup, whereupon you can pretend that the empty cup is now full and the empty jug is now empty.