“The subject of the Bhagavad-gītā entails the comprehension of five basic truths.
First of all, the science of God is explained, and then the constitutional position of the living entities, the jīvas.
There is īśvara, which means the controller, and there are jīvas, the living entities which are controlled. If a living entity says that he is not controlled but that he is free, then he is insane. The living being is controlled in every respect, at least in his conditioned life. So, in the Bhagavad-gītā the subject matter deals with the īśvara, the supreme controller, and the jīvas, the controlled living entities
Prakṛti (material nature) and time (the duration of existence of the whole universe or the manifestation of material nature) and karma (activity) are also discussed. The cosmic manifestation is full of different activities. All living entities are engaged in different activities.
From Bhagavad-gītā we must learn what God is, what the living entities are, what prakṛti is, what the cosmic manifestation is, how it is controlled by time, and what the activities of the living entities are.” – Bhagavad Gita as it is, Introduction