Choose a specific Challenge. You can pick a standard Challenge or one from any skill's individual description. For standard challenges, the challenge only applies to a specific task. So, for example, if you choose the Fast Task Challenge, you need to specify a task, such as the feint application of Bluff, or making an item with Craft. If you take Simultaneous Tasks, you need to specify the two tasks. Once specified, these things do not change.
You can perform the challenge chosen under this feat with a 5-point lesser modifier than usual. So, for challenges with a -5 penalty or a +5 Difficulty, you perform them like normal checks. For challenges with a greater modifier, you reduce the modifier accordingly. So a hero with Fast Feint, for example, can feint in combat as a move action with no Bluff check modifier (since the normal modifier is -5).
You can take this feat multiple times. Each time, it applies to a different challenge.