It's often said that one should 'trust your gut'.
On a practical everyday level, you might have some sense of how this works. If a situation or a person is a bit fishy, and you might not know exactly why often it turns out they are.
You might round a corner in your car, and slow down for unknown reasons, only to find that there has been an accident.
Our minds, actually most of our minds work on a mechanic called a 'neural network'. This is like a series of nodes, each representing a tiny particle of a certain sense, symbol, stimulus, thought, or process. The more these node are activated, the stronger the nodes signal gets.
That's the theory. In practice it's a bit like the state that you are in when you dream; all feeling, impulse, little thought and very symbolic.
What the majority of our mind operates on is a sort of 'transitive logic'. Rather than the connection between, say two things, like a conscious operation might do, like say the connection between a given person, and their betrayal of you, the rest of the mind works in a more 'overall' fashion.
It doesn't seek out the direct, logical, or obvious and potentially explainable connections between things. Where the conscious mind seeks to 'model', the unconscious mind seeks merely to 'learn'.
Instead, it maps the 'connections between the connections between things'. Transitive logic works like this: the banana is yellow, the lemon is yellow and bitter, the lime is bitter, therefore the banana is related to the lime. It's odd, but it's powerful. And it 'floats' to the conscious mind, like a bubble from a pond.
Let's say there are ten things that are sometimes present when someone betrays your trust. Sometimes those things are present when people are trustworthy. Might be a tone, a gesture, a certain circumstance.
The neural network level of understanding will map conditioning, or learning between those things, and the betrayal of trust. When the total signal strength of all the 'nodes' is high enough, you will get a 'gut feeling', a remnant of the feeling you had previous times you had that experience.
Generally, this is accurate enough, to serve as informative most of the time. That is to say, most of the time your 'gut' is right, and you won't be really aware of why. It's not precise, or always accurate, but it functions on favourable odds; if it turns out not to be the case, that experience too will be logged as learning.
There are a wide host of processes in the brain that we are not conscious of, and not all of them work exactly in the sense of deep learning. Some are a combination.
How we ride a bike or walk is partially learnt this way. In a way that we aren't really aware of all the moving parts but 'just know'. Muscle memory.
The definition of the unconscious itself varies a bit. Some use it to refer only to the stimulus we are unaware of, rather than internal processes. In fact, much of our behaviour is partially unconscious, or perhaps even mostly; peoples ability to report on the causes of their actions is very low (See: Nisbett RE, Wilson TD. "Telling more than we can know: Verbal reports on mental processes").
This makes sense, as the higher mind, was the later evolution. It's an add on. Logically the majority of our brains do not operate like this.
The mere presence of someone activates all of our models of them, past behaviour and knowledge, without our really being aware of it; something called 'contextual priming' (See: Higgins ET, Bargh JA. "Social perception and social cognition").
Of course, it's apparent that any sort of trance state is a sort of instinctual or automatic state, and there is a wealth of evidence on the benefits of that state of mind.
But on a more personal level, whether it's fighting in karate, weightlifting or overcoming a phobia, it can be very powerful, turning the whole thought process off, and to quote a bunch of coked up marketing morons 'just do it'. To let the body go, to become a sort of witness, rather than a pilot.
This is not to say, that an impulse or feeling is always accurate. Or that wandering around in some sort of thoughtless fugue all the time is a good idea.
In my experience, intuition tends to be more accurate when I know my own biases and predilections better. And trance tends to be useful when it's an in the moment activity, whereas planning and problem solving require some of that higher function and it's bittersweet mix of existential dread and curious wonder.
Famous scientists have used dreams and impulses to solve complex scientific problems, like Einstein and Rutherford. This is the secret: such impulses are not merely bunk or brain fluff to be ignored. They are often complex webs of information far too subtle for our conscious mind to easily grasp. Not always but often.
They can be tips from the bizarre and secret intelligence inside of us, that works in ways we struggle to comprehend. Even dreams can clue you into surprising new information. When that small voice speaks up; ask yourself if that's a personal fear, desire or foible, or is it a key being offered up from a secret door?