Tattva in the context of "Tat tvam asi"

The Mahāvākyas (sing.: mahāvākyam, महावाक्यम्; plural: mahāvākyāni, महावाक्यानि) are "The Great Sayings" of the Upanishads, with mahā meaning great and vākya, a sentence. The Mahāvākyas are traditionally considered to be four in number, though actually five are prominent in the post-Vedic literature:

1. Tat Tvam Asi (तत् त्वम् असि) – literally translated as "That Thou Art" ("That is you" or "You are that"), appears in Chandogya Upanishad 6.8.7 of the Sama Veda, with tat in Ch.U. 6.8.7 referring to *sat, "the Existent," and contextually understood as "That's how [thus] you are," with tat in Ch.U. 6.12.3 referring to "the very nature of all existence as permeated by [the finest essence]."
2. Ahaṁ Brahmāsmi (अहं ब्रह्मास्मि) - "I am Brahman", or "I am absolute" (Brihadaranyaka Upanishad 1.4.10 of the Yajur Veda)
3. Prajñānaṁ Brahma (प्रज्ञानं ब्रह्म) - "Prajñāna is Brahman", or "Brahman is Prajñāna" (Aitareya Upanishad 3.3 of the Rig Veda)
4. Ayam Ātmā Brahma (अयम् आत्मा ब्रह्म) - "This Self (Atman) is Brahman" (Mandukya Upanishad 1.2 of the Atharva Veda)
5. Sarvaṃ Khalvidaṃ Brahma - "All this indeed is Brahman"(Chāndogya Upaniṣad 3.14.1)

Mahāvākyas are instrumental in Advaita Vedanta, as they are regarded as valid scriptural statements that reveal the self (ātmán), which appears as a separate individual existence (jīva), is, in essence, non-different (not two-ness) from Brahman, which, according to Advaita, is nirguna. In contrast, these statements are less prominent in most other Hindu traditions, which emphasize a qualified or dualistic relationship between the self and Brahman, whom they regard as saguna, often identified with Vishnu, Shiva, Shakti, etc.

Vaishno Devi (also known as Mata Rani, Sherawali, Trikuta, Ambe and Vaishnavi) is an unmarried form of the Hindu mother goddess Mahalakshmi, embodying the tattva of Mahasarasvati and Mahakali. Vaishno Devi is worshipped as a combined avatar of the trinity goddesses.