An interesting question!
How we experience the hypnotic trance is state-dependent, meaning whatever state of mind you are in, it can influence the depth, intensity, and duration of any trance experience. Essentially, I see it as reaching that nebulous state that exists in what is termed sleep states and consequently creating a bridge between the world of emotion and cognition!
We are primarily emotional beings and secondly cognitive ones. We have to make conscious sense of our subconscious processes, even though we have no idea what they actually are, and much of life's difficulty comes from our conscious and non-conscious subjective interpretations of life's feelings. One may say "I feel a little apprehensive," another, "I feel terrified." Our linguistic ability to describe feelings accentuates a direct communication (external and internal) between our understanding of words and the inherent implication at the level of emotion. This simply means there is a link between our words and our emotional understanding of them; the same goes for facial expression! Since emotion elicits cognition and cognition elicits emotion, there is an interface between the two. Some scientists believe this to involve a part of the brain called the dorsal striatum (caudate nucleus and the putamen).
So, hypnosis works by stimulating the sensory cortices that are involved in both cognitive and emotional processing, essentially communicating with the brain, via the auditory cortex and stimulating our other senses remotely. Hypnosis occurs when the brain is in specific phases of brainwave activity i.e. theta/REM/NonREM2, 3, which are modulated by PGO waves and a reduction of norepinephrine from the locus coeruleus (the precursor to the stress response), akin to those of nighttime sleep and this facilitates the necessary changes in gene expression, which create an alteration in the way memories are both restored and activated (consolidation and reconsolidation) which eventually adapts the responses to meet the clients demands. This is a very complex biological process but that just adds to how amazing the brain is because our language allows us to reprogramme the way our brain functions. Evidence to support that can be felt when someone says something very pleasant or very unpleasant, either can elicit great changes in the way we feel!