All MindTouch sites have a way of organizing content hierarchically. Therefore, the standard navigation for the site is a left-hand nav bar that allows you to traverse the navigation tree easily. Here's how it works.
Navigating by expanding and collapsing the navigation tree
First, locate the nav tree on the left hand side of any page. You can expand any node that has a + sign (plus-sign) next to it. When you do that, you'll see all of the pages that live under that page. You can keep expanding sections without having to actually visit that page, just to see what pages are underneath.
By the same token, users can also collapse any node by clicking on the - sign (minus-sign) next to it. When you do that, the pages under that page will no longer be shown and the navigation tree becomes smaller.
When you've found the page you are browsing for, click on it to navigate there. When that page loads, you will notice the navigation tree automatically opens up to that page showing all of the pages it has as siblings as well as any of the nodes that might be its descendants.