What Is Online E-Billing / Invoice System?

I've updated the title of this thread from 'discussion' (does not give an idea of the discussion) to something that tells reader what to expect in the underlying discussion.

I'm not sure whether there's a definition. It's simply an automated system that creates invoices/bills online during an online commercial transaction and also processes payments online (through paypal, internet gateways, credit/debit cards, netbanking etc.). If you've ever bought anything on the internet, the chances are you've already been through an e-billing or online invoicing system.

Does that answer your question?