The one who believes in the existence of God, is said to be a ‘theist’, the one who accepts His dominance, is said to be a ‘religious’ and the one who feels bonded to Him, is said to be His ‘devotee’.
Love is generally defined through its expression reflected in our behavior. These behavioral strings, if attached with God make our earthly life infinitely beautiful. A devotee who stays calm in every type of situation, taking it to be His Lord’s will, is categorized as being in the passive mode- (shant bhav). He finds God as his guardian, on whom he is dependent for his every need. Saints, Yogis have this kind of mindset.
Next, there are people who feel an urge to lovingly serve God like a servant- (das bhav). They consider Him to be their master and remain occupied in the works which may please Him.
Thirdly, some devotees deal with God as a friend- (sakha bhav). This emotion brings the imperceptible Lord at the level of equality with us. Our casual behavior towards this friend lets us forget about the big Godly formalities and brings Him very close to our heart. Also, the world then looks like a playground on which God is playing the game of illusion (maya) with us. It is all for fun sake to be rich or poor, to succeed or fail. The moment we forget about this fact, we fall into the illusive trap and get away from Him. However, He, as a true friend, comes to our rescue and tries to remind us of the reality through His other playful tricks.
Further, there is a way to love God not as our creator but as our child- (vatslaya bhav). This sentiment detaches all ideas of power from the concept of GOD and gives us full freedom with Him like a parent. It is represented in the form we pamper Baby Krishna on Janamashtmi and Baby Jesus on Christmas. Yet, the ultimate form of love is said to of conjugal love and this too can be felt for Amighty- (Madhurya Bhav). Here, it is not about being male or female as God is beyond this differentiation. It is about being in passionate love with Him, the way Meera Bai considered Lord Krishna as her beloved.
Nevertheless, these set of feelings are not mutually exclusive rather perfection of one leads to the fusion of all the others in it. Think of a dedicated wife who loves her husband as a lover and takes care of him as a child too while serving him food or maintaining his clothes. She serves him by doing various household chores like cooking, washing, cleaning etc. She speaks her heart to him in the capacity of a friend and remains happily contented howsoever her husband may keep her. In the similar manner, we can feel bonded to God in all the above ways if the intensity of our only one bond reaches its pinnacle.
Ref- Bhakti Yoga, by Swami Vivekanand.