This Block creates a dynamic Table of Contents (TOC) for the Course - a list of all visible Sections (Topics or Weeks).
Clicking on one of the TOC links will display that particular section on the course page.
Although the features can be paralleled using the Navigation Block for example, this plugin does provide some additional control and options that mean it could still add something 'new to the mix' in the way it can pull the Section names, and/or the Section Summary (description) and cleverly use HTML heading styles to build the Table of Contents.
If providing users with simple navigation through long courses is something that is vital for your site then this could be a worthwhile plugin to investigate
You can try this Block yourself for real on our public plugins site: http://plugins.moodlebites.com