The Webform Paypal module sends the user to Paypal to complete a payment whenever they submit a webform containing the component on your site.
This module does not directly integrate with Paypal's APIs.
This module allows a site user to generate a Paypal 'Buy Now', 'Add to Cart' or 'Donate' button and replace their form's submit button with that button.
You can manually keep track of the payment status on individual submissions.
If the user doesn't complete the payment, your site will never know. Make sure to check for a completed payment with Paypal before sending a shipment!
If you need this type of functionality in Drupal 6, want more thorough integration with Paypal APIs, or use a different payment processor. Have a look at Webform Pay