Temporary (テンポラリー Tenporarī), as it name suggest, is a temporary place to put a card or ability that is being played. Unlike other zones, this zone does not physically exist on the playing field.
All Event cards (and by extension, the Event Ability) is put into this zone immediately after being played, and after its effect has been resolved, it is put into Trash afterwards. This is especially important when a player need to perform the reload effect in the middle of the resolution of an Event, so that the Event does not get mixed up with the cards in Trash when the player rebuild the deck.
Event cards that was played from any location other than the hand, or will be put in any location other than the Trash after being resolved (such as Event played by the ability of "Radiant Dragon, Innocent Star") is still placed in the Temporary before being put in the intended location afterwards.