The person-centred approach to counselling was originally described by Carl Rogers in the 1950's. His theory was that a self-directed process of change would follow from an individual's experience of a particular kind of relationship. This relationship was characterised by genuineness (congruence), non-judgmental caring (unconditional positive regard), and empathy.
Initially this type of counselling was known as 'non-directive' psychotherapy because it was based on the concept that counsellors cannot decide the directions in which people can change and develop. The approach was later called 'client-centred' or 'person-centred' to reflect the centrality of the client in the process of therapy.
Carl Rogers wrote extensively on the subject and several of his books are still available, 'On Becoming a Person' and 'A Way of Being' are two that may be of interest.