Narrative therapy is based upon seeing the client as the expert in their own life, also called client-centric. A narrative is a story that a person creates in order to give meaning to, and make sense of, their life.
All people do this, but if the person has encountered problems, the story can become focused on problems and dominate their life, and the person can suffer emotional and mental health issues.
In narrative therapy, the practitioner helps the client to examine this narrative, and whether it the story thet want for their life.
The therapist helps the client to focus on using the skills and abilities they have, to reduce the influence of problems in their life and create a new narrative that is more useful to them.