PayPal is an instant and secure online payment service that allows individuals and businesses to send payments through the Internet by credit card, bank debit card or check. According to PayPal, they have a customer base of more than 7 million and are the world's largest Internet-based payment network ("PayPal now constitutes over 10% of all Internet traffic in the financial services category, more than Citibank, Wells Fargo and Bank of America combined").

PayPal's roots are in the on-line auction community -- individuals looking for a reliable way to transfer money across the web. PayPal has recently expanded its services to commercial clients, like O-Hayo Sensei, and added support for international transfers.

PayPal is free to O-Hayo Sensei's customers (O-Hayo Sensei pays PayPal a percentage of each transaction) and PayPal handles all the transactions on their secure servers. Using PayPal requires joining their service (its free) and letting them verify your account information.