While you can cut a pizza with an ordinary knife, that’s hardly the best way to do it. You may have trouble slicing through the tough crust, and the toppings are likely to stick to the blade. You could end up with a ruined mess of uneven slices, torn and ragged crust, squished toppings, cheese and toppings dragged out of place, and areas that have no toppings at all. That’s not what you want, especially if you’re serving your pizza to guests!