From the SRD:
Activation
Wands use the spell trigger activation method, so casting a spell from a wand is usually a standard action that doesn’t provoke attacks of opportunity. (If the spell being cast, however, has a longer casting time than 1 action, it takes that long to cast the spell from a wand.) To activate a wand, a character must hold it in hand (or whatever passes for a hand, for nonhumanoid creatures) and point it in the general direction of the target or area.
Spell Trigger
Anyone with a spell on his or her spell list knows how to use a spell trigger item that stores that spell. Activating a spell trigger item is a standard action and does not provoke attacks of opportunity.