Filters can be used by selecting a filter from the filters drop down list in the toolbar. Filters can be edited by clicking on the 'Edit...' button in the filter toolbar, as shown below.

A filter is a predefined set of criteria which will be applied to any search which is performed.
Filters are useful when used as standard criteria in order to avoid performing more searches than are required.
For example, setting up a filter which contains the criteria: 'Notification Reason = C' will always make sure any search performed when that filter is turned on returns Coordination Request information.
When you click on 'Edit...' to edit the available filters, you are prompted with the following dialog:

The '(none)' filter is always present. This is used when you do not want a filter applied.
Filters can be added/edited/copied/renamed/removed/moved using the buttons provided. The search dialog box is used to define filters, but filters only contain criteria and no output fields.
Prompts are particularly useful when used in conjunction with filters.