The Upanishads, considered the bedrock of Indian wisdom and philosophy, are an essential part of Vedic literature and Sanskrit literature as a whole. They are complex and deep treatises that dwell on the knowledge of the self, reality, and the ultimate truth.

The Upanishads are not historical accounts or fables, but profound expositions of metaphysical and philosophical truths. The word "Upanishad" is derived from the Sanskrit root "Shad," which means to sit, with the prefixes "Upa" and "Ni" collectively implying sitting down near. The term therefore signifies the student sitting down near a spiritual teacher to receive esoteric knowledge.

These ancient texts consist of dialogues and discourses between learned scholars and their pupils, covering a broad range of philosophical and metaphysical subjects such as the nature of reality, the existence of the soul, the concepts of karma, Dharma, and Moksha, life after death, and the path to spiritual enlightenment.

In the Mahabharata, the Upanishads are often mentioned contextually. The Bhagavad Gita, one of the most important parts of the epic Mahabharata, displays a robust influence of the Upanishadic philosophies. Many doctrines articulated in the Bhagavad Gita, such as the immortality of the soul, yoga as a way to achieve spiritual enlightenment, detachment from material possessions, and the importance of performing one's duty (Svadharma), align with the teachings set forth in the Upanishads.

To put it succinctly, the Upanishads, as an integral part of Sanskrit literature, provide key philosophical insights into understanding the deeper meanings of life and the cosmos, guiding the individual toward self-realization and ultimately to an understanding of the divine. They form the core of Indian spiritual literature and have significantly influenced the theological foundations of Hinduism, Buddhism, Jainism, and Sikhism.