Under certain circumstances it might be useful to be able to send a link to one of your dashboards to someone not in the company/project. This where setting up a public dashboard can be useful. This allows someone with your link to look at the data displayed on your chosen dashboard without being able to edit the dashboard or gain access to data you do not wish to share. It is not a separate dashboard but you can create a dashboard to exclusively use for public display.
Public dashboards can be found at the bottom of the dashboard overview page (Dashboards in the side panel).
When you create a new public dashboard you first have to choose which of your dashboards you wish to share. After that you pick a link expiration date in the calendar below. A public dashboard with an expired link will be displayed with a red X-symbol and no longer be accessible.