The one which is all pervading, eternal and infinite is termed as Brahman also known as GOD. We human beings always look towards Him in our difficult times, thanks Him in happy moments and realize ultimately that we may discriminate our behavior with different people in our vicinity depending on their position, power and utility but GOD never does such discrimination. He is like a river which gives nourishment to every thing it passes though. It also gives water to every body that approaches it. But you know what even if a river do not differentiate while giving water- the seeker may get different quantity depending on the shape of his vessel.
Similar to this fact GOD also although do not make any differentiation, but different devotees come with different vessels of purpose and hence they get the same from Him accordingly. Therefore Bhagvad Gita has defined four different types of Bhaktas depending on their motives to approach GOD. They are as follows:-