The foam on the face of the slab is to be bricked. They simply burn or smash the foam to reveal the void. Personally, it was a crappy job on my alfresco and I chipped it all off and rendered it. Stupid idea with waffle slab.
Steve is correct, the foam you can see is used to form a rebate in the drop edge beam for brickwork under the porch and alfresco slab. The foam has been subsequently removed. It looks reasonably neat at the front porch but the alfresco is a bit crappy... the foam moved during the pour and the concrete lines are crooked.