En accounting terms, a direct debit is a form of payment that consists of communicating to the bank the payment of a certain amount of money at regular intervals. Thus, it is possible to direct the payment of bills (electricity, water, gas, telephone), of purchased goods (a computer, an appliance, etc.) or of a service contracted by subscription (to a gym, to a magazine, to a course, etc.).
Domiciliating one or more payments in the bank is a very comfortable form of payment, since the bank itself will collect the amount directly from your bank account, thus avoiding dangerous forgetting to pay your receipts or bills.