What is a concept? A concept as generally pointed out in these writings is something which we've taken as real but isn't. It's a useful idea but almost always refers something which doesn't actually exist. What are some examples?
Let's start with something easily seen through, like the seasons. We have Winter, Spring, Summer and Fall. Each of these has a specific start and end date - in the US we are witnessing the beginning of Fall. Fall is marked by a reduction in temperature (hopefully) - the leaves start turning colors (dying) and we are on our way to Winter. Is there such a thing as Fall, or Winter? No. There is nothing in existence of the sort, however we commonly use these concepts because we all agree on them. We know what we're talking about. We're referring something but that something isn't a thing at all. There is really no such thing as Winter, Spring, Summer or Fall. On Sept. 21 (or whatever date it starts), Fall will be here, but from Sept. 20 at 11:59 PM until Sept. 21 at 12:00 AM nothing actually changed.
We also have a concept for States in the US - California is a different state than Oregon or Wisconsin or Florida. California and Nevada share a common border. If you're standing in one spot, you might be in California, but someone just to the east of you may very well be standing in Nevada. You might even be able to reach out and touch them, however they are in a completely different state. If you look down, you don't see an actual border, no line drawn on the ground. It is an administrative border, not an actual one. If you stand straddled of the border, one part of your body is in California and one part is in Nevada. If you look from above via satellite, you see no real border. So the states are concepts - there really doesn't exist a separate state called California, a separate thing, but in the way we talk about them, we take them to be real, separate things in existence. This is the power of mind to create real, existent entities where there are none.
What about money? This might be a touchy subject. Is money real? What is it? If you go to work everyday, at the end of the week you might get a paycheck. Or it might be deposited directly into your bank account. All you see is an increase in your balance on the statement. The numbers in your employers account have reduced and your numbers have increased. So you can now go and pay your mortgage, buy groceries, either using a piece of paper called a check or by swiping a piece of plastic and signing your name. Numbers are transferred - you take some stuff home and the grocery store's balance sheet increases while your account reduces by a little.
If you go to the bank and ask for some of your money, what will you get? Some green pieces of paper with pictures of presidents, and some coins, or round metal pieces. Is this money? Does that green piece of paper and the piece of notebook paper have any more intrinsic value? No - it's still just paper. Only we have agreed that the dollar has more value - I can't trade the piece of notebook paper for an apple, but I can trade the green piece of paper for it. But it's still just paper. It has no value other than what we've agreed it has.
So where really is my money? For what can I trade the numbers or pieces of paper and metal? Maybe I can go to Fort Knox and trade it for gold? Then I have a bar of metal, shiny and heavy. Is that money? Where is the value in that? Can I break it apart and find the value inside? Can I squeeze the dollar bill and have the value drip out? No - the only value is what we've agreed the value is. Money is just representation of value - an agreed upon value - whatever we decide collectively that this piece of paper, or gold bar, or maybe cattle or sheep - whatever we agree has value we can barter with. So money is just a concept - it isn't a real thing in existence except what we agree upon.
So these are examples of concepts which don't actually exist except for a collective agreement. And then we might get lost in that concept - we might have trouble actually seeing through or accepting that there is no actual thing in existence called money. Or seasons. Or states. Or countries. Or any other concept.
We also have a concept called "mind" - is there such a thing in existence? Mind is a word, like money or Fall or California, which we've agreed to use to refer something. It refers to the thoughts, the memories, images, imagination. It refers something but is there such a thing or place called "mind"? Is it a thing in existence? Is it a place in the head, distinguishable with borders, attributes - maybe it's a gap in brain matter, a little box in which you sit, wired into all the senses, like a radio announcer's booth? Does mind exist as an actual thing? No - it's just a concept. A word collectively agreed upon to refer to something, yet it does not actually exist as a thing.
What about the concept of individual self? Is this a real thing or just a concept? What are the building blocks of the concept of individual self? The body, the mind, images, thoughts, feelings, emotions, stories, memories... So "individual self" refers these things - that concept refers to experiences, yes? There is nothing "subjective" about individual self - it is always something objective to you. It is a word or phrase or idea, like money, which refers to something but isn't a thing-in-itself, some "thing" which exists alone, apart. It is a concept. It refers to something objective, a field of experience.
So thoughts come and then another thought follows to bind the previous thoughts to the concept - "I am thinking" - so we have the thinking and then an "I" doing the thinking - this binding is another thought - or we can call that thought identification - tying in an obvious objective experience to the apparent subjective self. But this is where the concept trips over itself - is the subject part of the objective experience? Are you part of the objective experience? Where does that concept "individual self" start and end? The concept of individual self contains all the objective qualities, the experiences, but does it include the subjectivity? The knowing of the objective?
If we look, it certainly does include it. We include that subjective knowing in the concept of individual self. But if we apply the same inquiry into the reality of concepts, we might see that the concept of individual self is just a concept - it isn't actually a thing in itself - it is just a word referring something. Individual self, like money or seasons or states, doesn't actually exist as some "thing" but as an idea we've agreed upon. It's just a concept.
Therefore in any serious and honest inquiry - we must discern between what is a concept and what is real. What is actually in existence or what is just an idea. You know that you exist. You must exist to deny existence. But what, in this so-called world, exists as real and isn't a concept? If we truly look at the world we see that it too is just a concept for experiences, a box we use to quantify, an idea which is useful but doesn't actually exist a thing in itself. We might see that all objectivity is concept.
The only "thing" we can truly point to as real, as not a concept, is your Self. That presence of knowing which we might call subjectivity - the knowing of the objective experience - that is truly what we mean when we say "I AM". But that "I" is mixed up with the objective - tied up with concepts. So we discern between the conceptual and the real. We negate all that is conceptual until we arrive in inquiry at what is truly ourselves.
When that "individual self" is seen through as just a convenient concept, the certainty of your Self is still there - it is obvious and already known. We know it as "awareness" - but once again "awareness" is mixed up in that concept of individual self, a function of the individual self, "I am aware". When the individual self is seen through as just a concept, a useful label, then this "awareness" is something entirely outside that concept. It is a fullness, a capacity, an opening, an absence of anything particular, a background upon which these concepts play.
This true Self is a wide-open, vast, boundless reality of experiencing, an unconditional effortless potentiality which is always the case, which doesn't need to be achieved. It is already your Self except for the insistence on blending your Self with these concepts. It is simply the capacity for all experiences. It is the touchstone of reality in all experiences.
You are boundless awareness. Your true "Self" isn't a thing among things, not a finite thing in a world of things. Just as money, states, seasons are all useful ideas but don't actually contain reality, the individual self is just a nice idea, a stubborn concept - but if we can see through these concepts not really things in existence, then all concepts fall away - you are left only with your Self as the only reality. Then awareness is seen as just another concept, a useful pointer, and that concept isn't needed any longer.
Ultimately everything can be negated as a concept, except your Self, that which even the word "Self" fails to describe.