This extra allows you to give someone else use of a personal power. You must touch the subject as a standard action, and they have control over their use of the power, although you can withdraw it when you wish. If you are unable to maintain the power, it stops working, even if someone else is using it. Both you and your subject(s) can use the power simultaneously.
If the power only affects others, and not you, there’s no change in cost (a +0 modifier), essentially a combination of Affects Others and Limited (only others). You can increase the number of characters you can grant the power to simultaneously with the Progression power feat.