The navigation block is a feature of Moodle 2.0, The navigation block usually contains a sub heading of "My Home" with "My Moodle" "Courses" and the site Front page as links. The block's looks and location can be theme dependent. This block can also appear in a course. The navigation block contents depends upon both context and the role of the viewer.
The navigation block has links which can be expanded or collapsed. Here are examples of a 2.0 Standard theme's navigation block in collapsed mode and one that has the higher links opened one level.