This differs a lot by country and customer. For example, in Germany, without a fixed income, you’ll usually not get access to an overdraft loan.
In the US, overdraft is generally considered a very bad thing (almost worse than the idea of credit to Germans!) and a failure of the accountholder to “balance their (figurative, today) checkbook”, and the idea of an overdraft limit as a line of credit with a defined interest rate does not exist at all.
Yes, I was highlighting the difference with the US system.
Another difference is that if you know someone's account number, you can send them money but not take any out of their account. I understand it's more or less the other way round in the US.
In many European countries, "anybody" can take money out of your account, but you can return a direct debit for up to 13 weeks in case of unauthorized payments, and for 8 weeks for no reason whatsoever (including you just feeling like spending the money on something else).
Practically, the bank allowing a merchant to submit direct debits takes on significant credit risk as a result, so they grant that permission pretty carefully, similarly to how card processing merchant accounts require some level of trust.
In the US, overdraft is generally considered a very bad thing (almost worse than the idea of credit to Germans!) and a failure of the accountholder to “balance their (figurative, today) checkbook”, and the idea of an overdraft limit as a line of credit with a defined interest rate does not exist at all.