This gauntlet when worn on a hand acts as a shield (2 Armor) that can be used with Armor and your free Deflect action.
They also enable you to make a ranged (6 sq) attack for 1d4, 4 times per encounter. This ability needs to be manually reloaded (one action).
You cannot use the hand equipped with the Shooter Gauntlet for other purposes (like holding / using items).