Use-Activated Item

This type of item simply has to be used in order to activate it. a character has to drink a Potion, swing a sword, interpose a shield to deflect a blow in combat, look through a lens, sprinkle dust, wear a Ring, or don a hat. Use activation is generally straightforward and self-explanatory.
Many use-activated items are objects that a character wears. Continually functioning items are practically always items that one wears. A few must simply be in the character’s possession (meaning on their person). However, some items made for wearing must still be activated. Although these items are sometimes Command Word Items, usually it means mentally willing the activation to happen. The description of an item states whether a command word is needed in such a case.
Unless stated otherwise, activating a use-activated magic item is either a Standard Action or not an action at all and does not provoke Attacks of Opportunity, unless the use involves performing an action that provokes an Attack of Opportunity in itself. If the use of the item takes time before a magical effect occurs, then use activation is a Standard Action. If the item’s activation is subsumed in its use and takes no extra time use, activation is not an action at all.
Use activation doesn’t mean that if you use an item, you automatically know what it can do. You must know (or at least guess) what the item can do and then use the item in order to activate it, unless the benefit of the item comes automatically, such as from drinking a Potion or swinging a sword.