PayPal is “a global e-commerce business allowing payments and money transfers to be made through the Internet.” It allows its users to create a secure account with their banking information in order to make transactions online. Funds can be transferred either in or out of your account, so essentially PayPal serves as an intermediary between merchants and customers.
PayPal is an acquirer, performing payment processing for online vendors, auction sites, and other commercial users, for which it charges a fee. It may also charge a fee for receiving money, proportional to the amount received. The fees depend on the currency used, the payment option used, the country of the sender, the country of the recipient, the amount sent and the recipient's account type.
In addition, eBay purchases made by credit card through PayPal may incur extra fees if the buyer and seller use different currencies.
NOTE: The Paypal and Paypal API (Original) functionality has been deprecated. As of 1.1.18 WSM has a few clients using the functionality, but no new clients will be added. Checking the box noted in the image attached will cause the PayPal functionality not to work.