Bhakti is usually introduced as emotional religion set against ritual or philosophy, and the contrast misleads, because the tradition treats devotion as a discipline with stages, techniques and a technical vocabulary.
Classical texts on bhakti analyse it into modes, borrowing the terms of Sanskrit dramatic theory: the devotee may stand to God as servant to master, as friend to friend, as parent to child, or as lover to beloved, and the last is treated as both the highest and the most dangerous. The devotional literature works these relations out in great detail, and the poetry of the Krishna traditions in particular adopts the position of the woman in love, including in poems written by men, which is a deliberate and much-discussed feature rather than an accident of convention.
The practices are collective and sonic. Kirtan and bhajan are sung in call and response, sometimes for hours, accompanied by drum and cymbals, and the sustained repetition is designed to wear down self-consciousness in a group faster than any individual could manage alone. Repetition of the divine name is a discipline in its own right, counted or continuous. Weeping, trembling, hair standing on end and loss of composure are catalogued in the texts as recognised signs of progress rather than as embarrassments to be suppressed.
What makes bhakti theologically significant is its claim about access. The path requires no Sanskrit, no ritual purity, no priest, no wealth and no ancestry, only love. The texts state this explicitly and repeatedly, and everyone at the time understood that it was a claim with social consequences attached.