The difference between INVOICE and BILLING in SAP.

Both are same in SD point of view.
- In SD terminology we call as Billing Document and
- In FI terminology we call as INVOICE.
- In MM again only INVOICE will be there for Vendors.
Invoice is document indicating to delivery goods and Billing is a receipt of
payment.
If we receive the goods from vendors that is called bill if we give the
goods to customer that is called invoice. 
Bill means we have to pay the amount against bill invoice means we have to
receive the amount against invoice.
Invoice is for both : Vendor Invoice and Customer Invoice.
Billing Tcodes:
-  VF01 create billing document. The delivery order comes up auto.
-  VF02 the billing doc comes up auto . View the accounting enteries
  
Invoice Tcodes:
-  FB60 Create invoice with respect to rawmaterial and tax.
-  FB70 Invoice entries with respect to sales and tax