The term Unconditional Positive Regard comes from Carl Rogers.
His work is clearly outlined on the Simply Psychology website.
Everybody, says Carl Rogers, has the potential to make the very best of who they are. They will try to achieve that unless their self-image or their environment works strongly against it.
Those who have the best start are those whose parents offered them unconditional positive regard. They accepted and loved their child for what he or she was. This positive regard was not withdrawn if they did something wrong or made a mistake.
Such an upbringing engenders a sense of self-worth which in its turn encourages others to offer continuing unconditional positive regard and so on in an upward spiral.
Those who had a less accepting childhood can benefit now from receiving such unconditional positive regard. It offers them the environment in which they can take risks, move out of their comfort zone, and so find new aspects of themselves. The more self-worth they develop in this process, the more they will move toward achieving their full potential.