It's a site map. I don't know how to define it, but almost every website used to link to them at the bottom, and there you would find links to all areas of a website.
Process of elimination tells you the same. Web navigation is moving from webpage to webpage. A drop-down menu is just a pre-defined list available in one area. Bread crumbs are a trail showing the path a user has taken before arriving at a given page.
