That means that as you step from page to page, drilling deeper into more specific topics, the page tells you how you got there, and naturally how to get back. You'll see this most commonly on search engines such as Yahoo. Using our road map metaphor, though, this kind of navigation would look like a radial pattern of roads emanating from a single source and rarely crossing each other. To change directions, you must backtrack to the fork in the road that goes the way you want, and that can mean going all the way home before striking out again. Global and local sites work best with a navigation element that allows easy cross traffic.
Global navigation goes sitewide, whereas local focuses on a specific, topical area of the site.
It's the equivalent of a large road map, which in turn may have insets for a close-up of a specific town. Mix and match navigation schemes for optimal useability. The most common way of achieving this is with the navigation bar. Because it is so overused, every single person who has spent more than a few minutes on the Web knows how to use this thing. Many sites put it along the left side.