Purpose of PO Output for communication program

We have a requirement to stop the PO Output for communication from triggering between the approval stages. We only want POOC to trigger initially and at the final stage of approval. So, first we would to like to know the purpose of POOC. Is it only to generate the PDF document or to generate and send an email communication to the suppliers.

Hope email communication to the suppliers is based on their transmission methods set up in the supplier site level.

Please some one clarify our understanding.