When starting to learn about eCommerce you have to be familiar with the popular online payment processor PayPal.
PayPal has a free shopping cart which is one of the easiest and least expensive ways of building an eCommerce site.
Even if you use a full-featured shopping cart such as ZenCart, ZenCart will need to interface with payment processor. And PayPal is one such payment processor that can integrate with PayPal.
Depending on your needs, Paypal as four main product lines of various cost and fees: 1) Website Payment Standard, 2) Website Payment Pro, 3) Express Checkout, and 4) PayFlow. See our tutorial on the various PayPal products.
Paypal has a certification for web developers. If you pass this certification, you can claim yourself as a "PayPal Certified Developer" and be listed in PayPal Certified Developer Directory. More details about PayPal Certification here.
The best way to learn about PayPal is to sign up for a PayPal account and start using it. If you are a website merchant that is having an web developer/contractor setting up your ecommerce site, you may want to consider setting up contractor access or temporarily change your PayPal's password temporarily for your contractor.
You can find more PayPal tutorials in our tutorials section.
