Screens, or dashboards, are used to combine multiple reports, forms and charts into a single page. They are great for providing a snapshot of your data.
Screens use the concept of "master-detail". A master resource will determine what is displayed in a detail resource.
For example, lets say we have a report of libraries that included the state for each library along with the number of books by category. In the accompanying column chart we might show the number of books by category by state. Next we make the chart the master (parent) of the report. If we click on a particular state in the chart, the report will change to show information from only the same state.
See a screen sample here .