Buying the "physical" edition at retail gets you a box containing a download code. You redeem the code and download the game the same way a digital buyer would. There is no disc in the case.
Three practical consequences. First, storage: you'll need the full game's space free on your console regardless of which version you buy — a disc won't offset it. Second, internet: you need a connection to download, so a slow connection means a long wait on launch day. Third, resale and lending: a code, once redeemed, is tied to an account — the box can't be resold or lent the way a disc could.
Digital pre-orders can pre-load starting November 12, a week before launch, so the game is ready to play at release. Pre-load behavior for redeemed codes depends on when you redeem — redeeming early puts you in the same position as a digital buyer.
Plenty of players buy physical specifically for the disc — for resale value, for offline installs, or simply for the shelf. Knowing before you order that this box holds a code, not a disc, is the difference between a fine purchase and an annoyed one.