Pre-Orders are orders that a customer places for a future time. (Ex. Today is Wednesday and I want the order to be available on Friday at 5:30pm)

The order will show up on your tablet as a pre-order. Once it's time to make the order (get it ready), the pre-order will automatically convert into an active order and will show up as entirely new order so your staff won't miss it. 

It's easy for you to turn on or off if you want to allow pre-orders. Just go to Setting and Set up under Location Settings and check the box if you want to allow them.