Missa:
I really don't understand bank holds. lol
A "hold" is when a merchant puts a reserve on your credit limit because they don't know yet what your final total will be. For example, if you go to a gas pump and slide your card, the station doesn't know how much gas you will be pumping yet. So, it puts a "hold" of around $75 on your card's limit (and with that, makes sure that you do indeed have that much available). After you finish pumping, the actual amount gets charged and the "hold" is removed.
Restaurants do the same thing since when they swipe your card, they don't know how much of a tip you will add. So, the put a "hold' for the check amount plus 25%. Once you add the tip to the receipt and sign it, the "hold" is replaced with your actual total.