Do you understand how a merchant account works?
It’s not exactly like a bank account, because that’s more of a one-on-one situation where you put in money and then take it out again. Merchant accounts are “products” that your bank wishes to sign you up for, but not all banks actually deal with the funds themselves.
No, a merchant account is a middleman. You send them the credit card information and they feed it into their system to make sure that no fraud has been reported on this line and it does appear to be a genuine customer-held credit card. They encrypt the information for security as they send it over. Then once it has been processed, it goes to the bank that actually provides the funds, and then you have your purchase.