Devotion, in its simplest form, means addiction to God. While ritualistic adoration is done through the gross body, devotion is the advanced stage of passionately adoring Him by all means. A devotee's mind is found continually engrossed in God and so virtually absent from the world. This sort of obsession soon takes the form of Divine love as all the senses wish to savour Him only.
Also, devotion involves unconditional surrender and for that reason, devotees do not seek any change in the course of their destiny. Instead, they pray for strength to faithfully accept everything as a pre-set arrangement of Providence. In fact, our addiction to our Idol naturally make us indifferent to the worldly sorrows and joys. How can a drunken lover sense anything else than his beloved? In this way, devotion lifts us up from the physical plane and attaches to Him by permeating whole of our being with eternal bliss.
To conclude, Gyaan makes us realize the impersonal form of God, Bhakti provides for His perosnal attainment and Prem lets us take delight in Him.