Form Tools comes with two types of filters: Standard filters, and Client Map filters. They provide you with two alternative ways to limit the submissions that appear in the View.
You may define as many filters as you want for each View. When you add multiple filters, all conditions have to be met for a submission to appear in the View. For example, if you define a standard filter for "state" to be "WA" and another for "City" to be "Seattle", the View will only contain submissions that are for Seattle, Washington - and none other.
The following two pages describe the filter types, followed by some examples of how they can be used.