The standard approach to menu dropdowns has each sub-category appearing under main menu when the top-level menu item is hovered over. With the Megamenu, all items from two levels deep are shown on hover with the menu stretching full width across the menu width.
Standard menu with single dropdown
Mega menu showing categories two levels deep
There are two Mega menu formats. The first shows categories two levels deep, while the second mega menu shows only one level deep, with the second level showing on hover. This is useful for sites that have many nested categories
Mega Menu option 1 - two levels deep showing
Alternate Mega menu option - with one level showing and the second on hover