Once a customer enters the credit card information, the merchant account provider (MAP) takes over. Your MAP will verify the credit card, process the transaction, and make the deposit into your account, usually within a couple of days.
If you already have a "brick-and-mortar" store, your MAP should be able to handle your online transactions as well but make sure to find out if there are higher rates for Internet sales because of the increased risk of fraud. You can shop around for the best values on fees since you can expect your MAP to charge fees for: your application, setup and individual transactions. You may also have to purchase point-of-sale equipment or software.
To learn more about the vital role credit cards can play on your site, read this article: All About Merchant Accounts
To find out the best way to accept plastic to your online business: Getting a Merchant Account