Dashboards in ion are visual representations of the data in ion. There are several built in dashboards (for Behavior, as an example) that are not customizable. However, the dashboard tool within ion is a customizable, flexible means of presenting data.
A dashboard is made up of widgets (or components). Those widgets may be canned "reports" (KPIS, Attendance, etc), or may be widgets that visualize data from a Data Wall. In general, the foundation of any dashboard is a data wall.