This is often referred to as the Hamburger Menu since the universal icon is three stacked horizontal bars, that look rather like a hamburger   , yum!

Since the Site Map Menu is multi-tiered, you can have as menu tiers as you like, it is a great idea to include all of your pages in your Site Map Menu. Therefore, your pages will be easily found. Site Map Menus are great for larger sites and of course mobile devices.