radha-krishna eka atma, dui deha dhari'
anyonye vilase rasa asvadana kari'
Radha and Krishna are one and the same, but They have assumed two bodies. Thus They enjoy each other, tasting the mellows of love.
The two transcendentalists Radha and Krishna are a puzzle to materialists. The above description of Radha and Krishna from the diary of Srila Svarupa Damodara Gosvami is a condensed explanation, but one needs great spiritual insight to understand the mystery of these two personalities. One is enjoying in two. Sri Krishna is the potent factor, and Srimati Radharani is the internal potency. According to Vedanta philosophy, there is no difference between the potent and the potency; they are identical. We cannot differentiate between one and the other, any more than we can separate fire from heat.
Everything in the Absolute is inconceivable in relative existence. Therefore in relative cognizance it is very difficult to assimilate this truth of the oneness between the potent and the potency. The philosophy of inconceivable oneness and difference propounded by Lord Caitanya is the only source of understanding for such intricacies of transcendence.
In fact, Radharani is the internal potency of Sri Krishna, and She eternally intensifies the pleasure of Sri Krishna. Impersonalists cannot understand this without the help of a maha-bhagavata devotee. The very name "Radha" suggests that Srimati Radharani is eternally the topmost mistress of the comforts of Sri Krishna. As such, She is the medium transmitting the living entities' service to Sri Krishna. Devotees in Vrindavana therefore seek the mercy of Srimati Radharani in order to be recognized as loving servitors of Sri Krishna.
Lord Caitanya Mahaprabhu personally approaches the fallen conditioned souls of the iron age to deliver the highest principle of transcendental relationships with the Lord. The activities of Lord Caitanya are primarily in the role of the pleasure-giving portion of His internal potency.
The absolute Personality of Godhead, Sri Krishna, is the omnipotent form of transcendental existence, knowledge and bliss in full. His internal potency is exhibited first as sat, or existence -- or, in other words, as the portion that expands the existence function of the Lord. When the same potency displays full knowledge it is called cit, or samvit, which expands the transcendental forms of the Lord. Finally, when the same potency plays as a pleasure-giving medium it is known as hladini, or the transcendental blissful potency. Thus the Lord manifests His internal potency in three transcendental divisions."
(Sri Caitanya-caritamrita Adi 4.56, Purport)