Here's what the Orbs CCG rules say:
"Each card is made up of various components: name, color, type, subtype, energy cost, card text, and, in the case of an ally, attack points (AP) and health points (HP).
You can't simply play any card you like. First, you must be able to afford its energy cost. Second, cards can't always be played, depending on the phase of the turn.
During your Defense phase, you can only play action cards from your hand, but not allies, objects, or traps. However, any card can be played from the Bench during your Defense phase. This gives you an the element of surprise, if you plan ahead.
During your Main phase, you can play any card that you have the energy to afford. A few cards require additional conditions in order to be played, such as having played at least two cards that turn. "