There are five areas of online credit card processing:
Customers Credit Card - Provides money used in transaction. All card are processed the same way. (Credit or Debit)
Shopping Carts - Used as a collection process for necessary data including credit card information, product types, quantity of products and shipping information.
Payment Gateway - Transfers data from shopping cart to merchant account. Searches for fraud and the overall authorization of the transaction.
Internet Merchant Accounts - Confirms the credit/debit account for funds. Transactions are processed, then funds are transferred to checking account.
Checking Account - Accepts funds from your online sales.