PayPal has two gateways - PayPal Subscriptions & PayPal Invoices.
PayPal Subscriptions is for automated subscription payments each month. For Example : You have a monthly Recurring Payment of 5.00$. You can automate the Payment to us, using the Paypal Subscriptions Service. Every Month when you payments will be due, Paypal will automatically debit your account with 5$ and Credit our Account by 5$. There are no seperate charges for this Service (both by us and Paypal). You will receive confirmation Email from Paypal aswell as from us.
PayPal Invoices is for those who wish to receive invoices each month and login to pay manually.