Radha-Krishna are collectively known within Hinduism as the combined forms of feminine as well as the masculine realities of God. Krishna and Radha are the primeval forms of God and his pleasure potency (Hladini Shakti), respectively, in several Vaishnavite schools of thought.
In Krishnaite traditions of Vaishnavism, Krishna is referred to as Svayam Bhagavan and Radha is illustrated as the primeval potency of the three main potencies of God, Hladini (immense spiritual bliss), Sandhini (eternality) and Samvit (existential consciousness) of which Radha is an embodiment of the feeling of love towards the almighty Lord Krishna (Hladini).
With Krishna, Radha is acknowledged as the Supreme Goddess. It is said that Krishna is only satiated by devotional service in loving servitude and Radha is the personification of devotional service to the supreme lord. Various devotees worship her with the understanding of her merciful nature as the only way to attain Krishna. Radha is also depicted to be Krishna himself, split into two, for the purpose of his enjoyment. As per Hindu scriptures, Radha is considered as the complete incarnation of Mahalakshmi.
It is believed that Krishna enchants the world, but Radha enchants even him. Therefore, she is the supreme goddess of all and together they are called as Radha-Krishna.