Look at it this way... If you order a pizza from Dominoes and pick it up, they don't deliver it to you, you have picked it up. So look at it as Domino's being the seller; you pick the pizza up and give them the money which is effectively cash on pick up. If you order a Pizza to be delivered ie; transported to your residency this is C.O.D; the driver gives you your pizza, you give them the money (Assuming it wasn't paid for over the phone or online)