There is a chance that site is using this: http://wpmegamenu.com/mega-menu/
I think you are looking for a mega menu. It might be worth searching on that
Thanks for the suggestion martcol but I already have this plugin and it doesn’t do what the favim menu does.
I was thinking how you might be able to accomplish this with css and I think you could make the div with the menu in it and get it to appear as a relative position element via a transition CSS command but you can’t really control how the CSS redraws its transitions so I doubt you could get the “slide down” effect that make this type of menu desirable for me. I’m sure this is some type of javascript/jquery, both of which I am hopeless at so its some type of plugin for me.