I'll use Derrick Rose as an example. Do you want the ON BALL defender to go over the pick (try to take away the shot, give up the drive), go under the pick (give up the shot, take away the drive), or switch (keep a defender in front of Rose, but potentially switching to a defensive disadvantage)?
Hedging: Do you want the OFF BALL defender (man guarding the screener) to Hard Hedge (he will cut off Rose as best as he could THEN get back to his man which will leave you open to a pick a roll to the basket). Do you want him to Soft Hedge (Off Ball defender will flash at Rose but quicker get back to his man to defend either the pick n pop or roll...but rose may still be able to get to the basket with ease). Do you want to Double (Off ball defender will forget about his man and trap Rose which will leave you open to the roll and pop)
Hope that helps