Here is a short explanation of the difference between the two types of ads:
Page Post: I want people to engage with my Facebook page or comment as much as possible, and show my ads to people who are most likely to engage with my page.
Traffic: Tells Facebook, I don't mind who sees my ad, show it to everyone in the area.
These ad types generally don't require you to have as high of a budget. If you would like more info on these ad types and how they can work for you, register for the Ad help and performance review session.