Definition - What does Radha mean?
Radha is a Hindu goddess who is also sometimes called Radhika, Radharani and Radhikarani. She is almost always depicted with the Hindu god Krishna, an avatar of Vishnu. In the Indian sects of Vallabha and Gaudiya Vaishnava, Radha is regarded as the original goddess, or shakti. These sects worship Krishna as the Svayam Bhagavan, or the Lord himself, and Radha is acknowledged as his supreme lover — the supreme goddess. She's believed to control Krishna with her love.
In Bhakti yoga, or the yoga of devotion, the goddess Radha is very important. She is considered the entrance to the union of souls and the sacred.
Yogapedia explains Radha
In the traditions of Hinduism that focus on Krishna, such as the Vaishnava and Bhakti traditions, Radha is said to be Krishna's favorite among the gopis (cow-herding maidens), who were all in love with him. She was his friend and advisor.
For some of the adherents of these traditions, her importance approaches or even exceeds that of Krishna. She is also considered the incarnation of the goddess Lakshmi, who is the consort of Lord Vishnu. It is believed that one who chants "Radha" with a pure heart is accompanied by Krishna. Her importance and superiority is also given by Krishna's flute, which repeats her name.
There's a well-known Hindu term, Radha Krishna, which refers to the combination of both the feminine and the masculine aspects of God.
The practitioners of Bhakti yoga are devotees of the love between Radha and Krishna, the feminine and the masculine. However, it's Radha alone who's believed to be able to open hearts.