A dashboard is a view of type print that has been flagged as a dashboard and that has Companies as a starting table. Dashboards are used in the homepage to display aggregate and overview information. They can be managed directly in the homepage using the Dashboards > Manage dashboards context menu or they can be built from Forms & Views.
To flag a print as a dashboard you must check Available as list / print / dashboard and Available in the backoffice in the options. This ensures that the dashboard is selectable from the left context menu in the homepage. If you create a dashboard directly from the Lists > List management context menu then the flags are set automatically.