Bhakti yoga is one of three yoga taught in Bhagavad Gita. Bhakti means we must surrender to Krishna alone. We all have a natural and original transcendental relation with Lord Krishna. To engage in that relationship under the guidance of a bonafide spiritual master is called bhakti or devotional service. Bhagavad Gita is the dictionary and Srimad Bhagavatam is the encyclopaedia to properly understand the process of bhakti-yoga.
Aarth Bhakt: The Bhagavad Gita, recognizes four kinds of devotees who practice Bhakti yoga. Some practice it because they are hard pressed or stressed by anxiety or their life’s circumstances and see Bhakti yoga as a form of relief.
Jigyasu Bhakta: The second type practices Bhakti yoga to learn about god out of curiosity and intellectual intrigue.
Artharthi Bhakta: The third type seeks rewards in this or in the afterlife through their Bhakti yoga.
Gyani Bhakta: The fourth are those who love god driven by pure love, knowing and seeking nothing beyond that experience of love union.
According to these Hindu texts, the highest spiritual level is the fourth, those who are devoted because of their knowledge of love. The Bhagavad Gita states that all four types of Bhakti yogi are noble because their pursuit of Bhakti yoga sooner or later starts the journey on the path of spirituality, it keeps one away from negativity and evil karma, it causes spiritual transformation towards the goal of Bhakti yoga.