On the other hand we have the purely physiological definition of emotions, as a make up of a number of neurotransmitters. We also know that emotions create memories. On a tridimensional model, we can create or retrieve a memory (or the beginning of it) at the intersection of specific concentrations of these three neurotransmitters. The more intense the emotions, the higher the concentration at intersection, the longer lasting and ease of retrieval of that memory.
Feeling or the sense of urgency is what remains on a short term from an emotion undealt with right away for various reasons.
Memory is what remains after the dimming of those feeling. Feelings can be recreated by accessing that memory that helps bringing up all the details. Both feelings and emotions are an evolutionary necessity.
An individual can remember when at ease what happened at a certain moment and deal with it if still possible or share the experience with the group.
Conscious evaluation of those feelings, sometimes by just sharing them and sometimes with the help of a therapist that is trained to help retrieving them helps putting them to rest or quenching them with .
We can see both emotions and feelings are part of the unconscious mind.
Freud was an Austrian Jewish therapist, founder of modern psychology though its branch psychoanalysis. During the late decades he was largely marginalized due to advent of chemical psychiatry.
Freud shared with us his undeniable highly successful therapy experiences though which he discovered one of the most important aspects of psychology, something named by him transference.
On short, by generalizing his definition, feelings undealt with can transfer from towards the initial object, situation or person to another, if somehow enough unconscious stimuli that lead initially to those feelings thus triggering the same combination of neurotransmitters can be recreated.
That may be evolutionary also because people while socializing may voluntarily share or helped to remember situations, how they dealt with, helping the members of the group to deal with similar situations if repetition is suspected possible.
However human socialization rules have changed very fast during the last millennia especially in differentiated societies (like with classes). People have learned to keep their experiences and thoughts to themselves more than in the past, this bringing to them a survival advantage. That evolutionary function of human behavior, sharing of memories, started to be suppressed, individuals accumulating undealt with emotional experiences.
Children of the civilized families let's say in Freud's Vienna often did not have an opportunity to share their intimate thoughts with their parents maybe because such sharings where considered inappropriate and sometimes they carried for a long time their negative experiences exactly with those who they normally were supposed to share, never having an opportunity to quench their feelings.
Why transference has such importance, not only in psychology but mostly in psychological warfare.
Emotions, feelings and even memories are uncontrollable.
By intentionally creating a combination of stimuli similar to those created by the sharing of an experience by an individual to the group the old fashion, ancestral way; using some elements of the experience, and adding some new information of their own, an interested entity may be able to create similar emotions and cancel or suppress the memory of those shared thoughts, substituting (transferring) in the mind of a person or even a large audience (in a subliminal or hidden, unrecognizable fashion) the shared situation with something else, related semantically, and with this suppressing or twisting any memory that can bring ideas that may be a disadvantage to them.
Transference also occurs frequently with showing in media of persons in power (TV presenters, politicians) postures, substituting for fathers and mothers, or intimate postures, substituting for lovers, postures that may also carry direct or hidden (subliminal), undeniable (by perception) messages.