Bhakti is a Yoga of devotion or complete faith. This faith is generally in the God or supreme consciousness in any of the forms. It may be Lord Rama, Krishna, Christ, Mohammed, Buddha etc. It may be a Guru for his disciples. Important thing is the person interested in following this path should have very strong emotional bond with the object of faith. The flow of emotional energy is directed to this object. Mostly people suppress their emotions and that often reflects in the form of physical and mental disorders. This Bhakti Yoga releases those suppressed emotions and brings the purification of inner self.
Continuous meditation of God or object of faith gradually decrease the ego of the practitioner, which further prevents new distractions, fickleness or even pain and induces strong bonds of love. Slowly the practitioner looses the self identity and becomes one with the object of faith, this is a state of self realization.