When you create a filter at the dashboard level, it applies to all of the reports within the dashboard. If a filter on the same field is present on a report in the dashboard, the report filter will be hidden when the dashboard is in the end user view. This relationship is shown in the dashboard editor by drawing a strikethrough on the report filter to indicate that the dashboard level filter takes precedence:

For the above example, the end user view of the dashboard looks like the following:

You can also create filters at the page level. For example, in the following dashboard, you might want to apply a date filter on the History tab only:

You'll want to create a nested page on the History page to contain the filter. Click on the Edit link next to the History page and do 'Add Sub Pages'. This action will create a nested page. The page controls won't show since there's a single tab, but you can create filters at this page level. To create a filter, click on Page Options -> Add Filter:

The resulting filter is only shown on the dashboard when you navigate to that particular page.

Next, let's dig into a further example on the History page. We might want to have a Date filter on the History page, but that date in turn needs to map to Date Created on one report and to Date Won on a second report.

Within the editor, you can click on the report level filter and choose 'Link to Dashboard Filter':

The window that pops up gives you the list of possible dashboard filters you can link the report filter to:

When linked, the dashboard level filter will be applied to the report using the report level filter's field. So in this case, even though the dashboard level filter isn't on Date Won, it'll map to Date Won when it runs at that report level.