A merchant account is a type of bank account that allows businesses to accept payments by debit or credit cards or bank transfers. It is a line of credit extended to businesses by the bank, after due risk assessment.
End users can apply a chargeback and retrieve the money back, if the business fails to deliver the promised service. And the line of credit extended by bank is used to reimburse such chargebacks and recover it from business. This is why there is a risk assessment of business and certain restrictions are applied on a merchant account, unlike a standard bank account