Direct debit is a kind of payment orders (instruction to transfer money) from your checking account (current account). The main difference is what Direct debit is an authorization for a person/organization to take payments from your account when they are due (see also standing order).
It authorizes some organization …
Overdraft is an amount that you can withdraw from your bank account or card in credit.
Not all bank accounts allow overdrafts. It can be set like a limit at your account or card.
Technically, an overdraft is a paperless loan attached to your checking account (current account, debit card …
Payment order is a paper or electronic order (instruction to transfer money) from your account.
Payment order you should create when you buy anything in Internet or pay for something from your bank account.
There different types of payment orders: