The idea of a Cognitive Filter is that we all - consciously but more usually unconsciously, view and experience the world through our own unique perceptual framework which often reinforces our established points of views. We are all guilty of it.
The best way to imagine a Cognitive Filter is a 2X4 jutting out of our forehead, from which we hang countless prejudices, prisms, bits of colored glass, polarizing filters, ornaments, whatever prior experiences we have had in life. Not only do we hang things, but for a great part of our lives - think childhood, think politics, news, education, friends and family - we allow other people to hang things there as well. Very often this 2X4 becomes so cluttered with "filters" that our vision is obscured unto blindness.
The funny thing about Cognitive Filters is that while none of us can see our own, or very often even the world past our own, we for some reason think we are able to see others. For example, we all recognize bigots, racists, homophobia, we can all look at our friends and say "this is your problem...", and our advice very often is good - we can see their problem, we've swung our own 2X4 far enough out of the way to take a clear look at theirs. Not always, and never as well as we think, but often enough. And often we can see a filter on their 2X4 - the same one we've hung on our own - and out of embarrassment refuse to observe it - Alcoholics, for example, generally out of politeness or a matter of form won't acknowledge that another person is an alcoholic - it's easier to ignore that filter and instead put their problems down to one of a thousand other filters hanging down from the 2X4, or we might recognize a filter on another and realizing we have the same one on ourselves flatter or congratulate the wearer - think of religion, politics, nationality, any number of clubs or organizations.
The point of all this meditation - "All This" so far rarely adds up to 30 minutes a day and never even a minute of true mind(ful)(less)ness - is to see past the cognitive filters and get back to an unencumbered view of the world.
...Or maybe I'm understanding it wrong...