In Theosophy and modern New Age beliefs, Djwahl Khuhl is one of the Ascended Masters. He was one of the main channels of information for both Madame Blavatsky and Alice Bailey. Therefore, a lot of the Theosophical theories are attributed to this Ascended Master.
Djwahl Khul is believed to have ascended fairly recently, i.e. approx. around 1900 AD.
He was a disciple of Kuthumi. (Both of them are referred to as the Tibetan Master).
Confucius is believed to be one of his previous incarnations.
Edmund Harold calls Djwahl Kuhl the Master of the 2nd Ray, which in his explanation is the Emerald Green Ray.
His fields of activity or expertise have to do with Healing and Altruism, and the expression of idealism in a practical way.
Note that nearly every author spells his name differently: Dwahl Kuhl, Djwhal Khul, Djwahl Kuhl, etc.