What is the science or knowledge of one's relationship with the Supreme Lord?

There are three truths regarding one’s relationhip with the Lord. These are knowledge about the material world, knowledge about the living entities, and knowledge about the Supecime Lord.

The Supreme Lord is one without a second, omnipotent, all-attractive, the source of all opulence and sweetness, and the only shelter of the living entities and material nature. Although He is the shelter of the living entities and material nature, He is always fully independent. His bodily effulgence is known as the impersonal Brahman. He created the living entities and the material world by His spiritual potency, and then as Paramatma, a plenary portion, He entered into the universes. In His form of opulence or aisvarya. He is Lord Narayana in the spiritual sky. In His form of sweetness of madhurya, He is Sri Krsnacandra, the beloved Lord of the gopis, in Goloka Vrndāvana. His manifestations and pastimes are unlimited. There is nothing greater than or equal to Him. All His forms and pastimes manifest through His internal spiritual energy.

The living entities are aware of the three energies among the many potencies of the Lord. One is His spiritual energy, by which all His pastimes take place. Another is His marginal energy, the living entities, by which unlimited living entities are produced and sustained. The other is His external energy. maya, by which all material objects, time, and activities are created.

Sambandha-tattva refers to the following relationships: the living entities toward the Supreme Lord, the Supreme Lord toward the living entities and the material world, and the material world toward the Supreme Lord and the living entities. If one properly understands sambandha-tattva, one becomes acquainted with knowledge of one’s relationship with the Supreme Lord. Persons who are devoid of knowledge of their relationship with the Supreme Lord can never become pure Vaisnavas.