CREATE A DIVERSION TO HIDE
Make a Bluff check to create a diversion and become hidden using the Stealth
Action: Standard action. A creature can take this action only once per encounter.
Opposed Check: Against a target’s passive Insight. The target must be able to see the creature creating the diversion. A creature can make the check against multiple targets at once, opposing the passive Insight of each target with a single Bluff check.
Success: The creature can immediately make a Stealth check opposed by the passive Perception of any target that failed the opposed Bluff check. If the Stealth check succeeds against a target, the creature becomes hidden from that target until the end of the current turn or until immediately after the hidden creature makes an attack.
So to answer your questions, the action type is Standard unless otherwise specified (There are powers that let you do this as part of the action). And the DC is the passive insight of everyone who can see you creating the diversion. The result is that you can then make a stealth check to hide until the end of your turn.
This really only works if you're burning an action point or have a minor action attack, otherwise it's a waste of a turn.