Ok so I dont have time to write everything – so in this post I am quoting Wikipedia (naughty copying) ..
The Upanishads – are late Vedic and post-Vedic Sanskrit texts that “document the transition from the archaic ritualism of the Veda into new religious ideas and institutions”.
It is the emergence of the central religious concepts within Hinduism.
They are the most recent addition to the Vedas, the oldest scriptures of Hinduism, and deal with meditation, philosophy, consciousness, and ontological knowledge.
Earlier parts of the Vedas deal with mantras, benedictions, rituals, ceremonies, and sacrifices.
While among the most important literature in the history of Indian religions and culture, the Upanishads document a wide variety of “rites, incarnations, and esoteric knowledge” departing from Vedic ritualism and interpreted in various ways in the later commentarial traditions.
Of all Vedic literature, the Upanishads alone are widely known, and their diverse ideas, interpreted in various ways, informed later traditions of Hinduism.
