An abreaction is a reaction, usually occurring during therapy, that is the expression and emotional discharge of subconscious memories and/or emotions.
These can happen spontaneously or be brought about purposefully during hypnosis.When brought on during hypnosis it can be used to acquire greater depth, cause a revivification or help to remove repressed emotions.
The emotion within an abreaction is very real, a person can feel the situation as if it is happening there and then, with all the senses that are involved in the situation - smelling the smells, hearing the sounds, feeling the pain etc.