A directmerchant account is a special type of bank account which allows the direct processing of credit cards, debit cards, checks and ACH. Most businesses that a have point-of-sale(POS) or point-of-purchase(POP) credit card processing unit or service have a direct merchant account. Online business and e-commerce websites also use direct merchant accounts.
To facilitate the transaction between the major credit card companies and banks and your business, a payment gateway is required. The payment gateway encrypts and handles all the communication between the merchant and the end users bank. Authorize.net and DataPayPro are examples of payment gateways.