The Content Map is there for you to be able to visualise the hierarchy of your project.
This shows the structure and relationship between Items in your project, as well as the current status of an Item.
You can collapse and expand any parent Item by clicking on it, and that will collapse all the children underneath it, to allow you to view the structure of your project at different levels. If you click on the arrow in the top right of a parent Item, you can view a subtree of just that parent and it's child Items.
To get back to your Project Overview, click on the title of the sitemap in the top left of the screen.