When a customer  clicks on an affiliate link/banner and lands on your site integrated with the click tracking code (or lands on a replicated site), the click tracking code sends a request to the server which replies a PAPVisitorId (a unique 32-character-long alpha-numeric string). 
This PAPVisitorId is saved in  cookies and it gets saved in the database of PAP/PAN if the click was associated with an affiliate.
The PAPVisitorId inside the database of PAP/PAN stores the following data:
  • merchant account id (in PAP it is always 'default1')
  • IP address of the customer
  • details of the affiliate whose link/banner was clicked
  • banner id, campaign id
  • date of visit
  • time validity of the particular PAPVisitorId (cookie limit that can be set inside the campaigns of PAP/PAN)
Even if a Standard Link (redirect) or Mod_Rewrite link is used there is a PAPVisitorId created on the domain where Post Affiliate Pro (network) installation resides.