Unconditional positive regard refers to the supporting, accepting, respecting and understanding of one another as individuals without judgement or criticism. This is different from unconditional love; unconditional positive regard does not require love or affection - it simply refers to acceptance of others whether you like them or not.
It is used in client centred therapy and allows the client to be as open and honest as they like in a judgment free environment. They can say whatever they want to and the therapist will be fully accepting.