what is significance of AGREEMENT_ACTION_COMPLETED webhook event

in my integration with adobe sign , I have subscribed to AGREEMENT_ACTION_COMPLETED &  AGREEMENT_WORKFLOW_COMPLETED
Based on those notifications , I am moving internal workflow , to better understand the sequence of events 

what is the difference between last signer's AGREEMENT_ACTION_COMPLETED event with respect to AGREEMENT_WORKFLOW_COMPLETED

Does adobe processes something at their side afrer AGREEMENT_ACTION_COMPLETED ?

My quick tests shows there is same time in both webhook  notification for "eventDate" in payload , See the attachment for payload screen capture for both notification.

Getting clarity on above will help.