They are more widely accepted than a personal check because they are “guaranteed funds”.
Any withdrawal from an account or a loan advance must be done by cashiers check. If the check is made out to the customer requesting the withdrawal there is no extra charge for the check. If the check is made payable to another party other than the customer there is an extra charge for this.
You may purchase a cashiers check if you want the added security of this type of check versus a personal check, or if the amount you need is more than the amount allowed in a money order.