Kṛṣṇa and the Supreme Personality of Godhead are identical. Therefore Lord Kṛṣṇa is referred to as Bhagavān throughout the Gītā. Bhagavān is the ultimate in the Absolute Truth. Absolute Truth is realized in three phases of understanding, namely Brahman, or the impersonal all-pervasive spirit; Paramātmā, or the localized aspect of the Supreme within the heart of all living entities; and Bhagavān, or the Supreme Personality of Godhead, Lord Kṛṣṇa.
(Bhagavad-Gita-----2:2-----purport).

"The Absolute Truth is realized in three phases of understanding by the knower of the Absolute Truth, and all of them are identical. Such phases of the Absolute Truth are expressed as Brahman, Paramātmā, and Bhagavān."
These three divine aspects can be explained by the example of the sun, which also has three different aspects, namely the sunshine, the sun's surface and the sun planet itself. One who studies the sunshine only is the preliminary student. One who understands the sun's surface is further advanced. And one who can enter into the sun planet is the highest.
(Bhagavad-Gita-----2:2-----purport).

Ordinary students who are satisfied by simply understanding the sunshine—its universal pervasiveness and the glaring effulgence of its impersonal nature—may be compared to those who can realize only the Brahman feature of the Absolute Truth. The student who has advanced still further can know the sun disc, which is compared to knowledge of the Paramātmā feature of the Absolute Truth. And the student who can enter into the heart of the sun planet is compared to those who realize the personal features of the Supreme Absolute Truth. Therefore, the bhaktas, or the transcendentalists who have realized the Bhagavān feature of the Absolute Truth, are the topmost transcendentalists, although all students who are engaged in the study of the Absolute Truth are engaged in the same subject matter.
(Bhagavad-Gita-----2:2-----purport).

These fragmental portions are eternally so, and even after liberation the individual soul remains the same—fragmental. But once liberated, he lives an eternal life in bliss and knowledge with the Personality of Godhead. The theory of reflection can be applied to the Supersoul, who is present in each and every individual body and is known as the Paramātmā. He is different from the individual living entity. When the sky is reflected in water, the reflections represent both the sun and the moon and the stars also. The stars can be compared to the living entities and the sun or the moon to the Supreme Lord. The individual fragmental spirit soul is represented by Arjuna, and the Supreme Soul is the Personality of Godhead Śrī Kṛṣṇa.
(Bhagavad-Gita-----2:13-----purport).

"Both the Supersoul (Paramātmā) and the atomic soul (jīvātmā) are situated on the same tree of the body within the same heart of the living being, and only one who has become free from all material desires as well as lamentations can, by the grace of the Supreme, understand the glories of the soul." Kṛṣṇa is the fountainhead of the Supersoul also, as it will be disclosed in the following chapters, and Arjuna is the atomic soul, forgetful of his real nature; therefore he requires to be enlightened by Kṛṣṇa, or by His bona fide representative (the spiritual master).
(Bhagavad-Gita-----2:20-----purport).

Consequently, Kṛṣṇa will now tell him about the working process in buddhi-yoga, or karma-yoga, or in other words, the practice of devotional service only for the sense gratification of the Lord. This buddhi-yoga is clearly explained in Chapter Ten, verse ten, as being direct communion with the Lord, who is sitting as Paramātmā in everyone's heart. But such communion does not take place without devotional service. One who is therefore situated in devotional or transcendental loving service to the Lord, or, in other words, in Kṛṣṇa consciousness, attains to this stage of buddhi-yoga by the special grace of the Lord. The Lord says, therefore, that only to those who are always engaged in devotional service out of transcendental love does He award the pure knowledge of devotion in love. In that way the devotee can reach Him easily in the ever-blissful kingdom of God.
(Bhagavad-Gita-----2:39-----purport).

To say that one is in samādhi is to say that one has fully realized Kṛṣṇa consciousness; that is, one in full samādhi has realized Brahman, Paramātmā and Bhagavān. The highest perfection of self-realization is to understand that one is eternally the servitor of Kṛṣṇa and that one's only business is to discharge one's duties in Kṛṣṇa consciousness. A Kṛṣṇa conscious person, or unflinching devotee of the Lord, should not be disturbed by the flowery language of the Vedas nor be engaged in fruitive activities for promotion to the heavenly kingdom. In Kṛṣṇa consciousness, one comes directly into communion with Kṛṣṇa, and thus all directions from Kṛṣṇa may be understood in that transcendental state.
(Bhagavad-Gita-----2:53-----purport).

He knows that his material condition of life is under the supreme control of the Lord; consequently he is not disturbed by all kinds of material reactions, which he considers to be the mercy of the Lord. According to Śrīmad-Bhāgavatam, one who knows the Absolute Truth in three different features—namely Brahman, Paramātmā, and the Supreme Personality of Godhead—is called tattva-vit, for he knows also his own factual position in relationship with the Supreme.
(Bhagavad-Gita-----3:28-----purport).

Being in a bewildered condition, therefore, the embodied soul identifies himself with the circumstantial material body and becomes subjected to the temporary misery and happiness of life. The Lord is the constant companion of the living entity as Paramātmā, or the Supersoul, and therefore He can understand the desires of the individual soul, as one can smell the flavor of a flower by being near it. Desire is a subtle form of conditioning for the living entity. The Lord fulfills his desire as he deserves: Man proposes and God disposes. The individual is not, therefore, omnipotent in fulfilling his desires. The Lord, however, can fulfill all desires, and the Lord, being neutral to everyone, does not interfere with the desires of the minute independent living entities.
(Bhagavad-Gita-----5:15-----purport).

The whole Bhagavad-gītā centers around the declaration that Kṛṣṇa is the Supreme Personality of Godhead. That is the version of all Vedic literature. Para-tattva means the Supreme Reality, who is understood by the knowers of the Supreme as Brahman, Paramātmā and Bhagavān. Bhagavān, or the Supreme Personality of Godhead, is the last word in the Absolute. There is nothing more than that. The Lord says, mattaḥ parataraṁ nānyat kiñcid asti dhanañjaya. Impersonal Brahman is also supported by Kṛṣṇa: brahmaṇo hi pratiṣṭhāham. Therefore in all ways Kṛṣṇa is the Supreme Reality. One whose mind, intelligence, faith and refuge are always in Kṛṣṇa, or, in other words, one who is fully in Kṛṣṇa consciousness, is undoubtedly washed clean of all misgivings and is in perfect knowledge in everything concerning transcendence.
(Bhagavad-Gita-----5:17-----purport).