The project overview shows all the projects you have viewing access to. This is determined by the groups that have been selected in the permissions tab for each project. If you're an admin, you'll see every project.
Navigation
At the top of the page is the nagivation where you can create a project (assuming you have permission to do so), perform bulk actions if any of the project checkboxes are selected, and filter the shown data by searching, selecting a specific category or publishing state. The publishing state filter will only appear if you have permission to edit, or edit the state of any project.
Clicking on a project title will active that project and redirect you to the dashboard overview.
The progress bars show the percentage of completed tasks belonging to each project, regardless of their publishing state. If a project has no tasks, the bar remains at 0% completition.
The viewing access label, which shows the groups that have access to each project, is only visible to admins.