Hiroo Hi!
Maestro and iDeal have nothing to do with each other. Because if you pay using iDeal, you're paying directly from your bank account. Your card isn't involved in this process, and you can pay something using iDeal without even owning a card at all.
iDeal is a Dutch online payment method to be able to pay online from your bank account. This system was put in place, because you're unable to do online payments with a Maestro card (at least in the Netherlands). Maestro is a type of debit card used in the Netherlands and Belgium. Maestro is owned by MasterCard.
There are other debit card solutions, like V Pay from Visa. MasterCard also has a "Mastercard debit".
Is there anything else you would like to know?