Merchant Account: Holding account for funds your receive or refund through your Internet payment gateway.
Payment Gateway: Web store will submit transactions to your payment gateway for processing. Browser based interface allows you to enter, void, refund, and capture credit card transactions. Web site -> Merchant Acc.
Security (SSL) Certificate: Your Web site must have a security certificate assigned to it in order for it to securely process credit card transactions through a Web page. This identifies your and encrypts transaction data.
Hosting: Your Web site must be placed on a Web server that is connected via a high-speed connection to the Internet. You will pay for hosting and all software your run from site.