Sometimes in Pathfinder, you've dug down incredibly deep. You're viewing such a particular set of students and you just want to remove all the filters you've set. In the example below, I've selected a bunch of filters (I'm viewing the performance of female IEP students on the 5ELA-M1-NOV12 assessment.
While you could theoretically click each of the green selections (clicking a "green" selection will deselect it), it would be much simpler to click the "Clear" button on the left hand side of the filters.
Additionally, I can move backwards and forwards through my selections if I only want to deselect certain things. The "Back" and "Fwd" buttons function exactly like a web-page and will move you backwards and forwards through your selections.