The Upanishads are a collection of religious and philosophical texts that originated in India. They were most likely written between 800 BCE and 500 BCE, and reflect the people's intention to shift the focus of religious life from external rites to quests that are internal and spiritual.
The books, each complete in itself, contain insights from various spiritual Indian figures. Due to the nature of the varied texts, they do not represent a consistent philosophy or worldview. Instead, they tell of the experiences, opinions and lessons of many different people.
The exact number of Upanishads is unknown, though it is currently thought that about 250 exist. Approximately 10 of those are thought to be the most ancient, important and authoritative.
The Upanishads came to be at a time when the society in India started to question Vedic religious order. Because of this questioning, some people entered a pursuit of spiritual progress. These people began to reject material concerns and gave up family life. Their speculations and philosophy were put together as the Upanishads.
The etymological origin of the word, Upanishad, roughly means "sitting down near." The meaning alludes to the action of sitting at the feet of the illuminated teachers to take part in sessions of spiritual instructions. This practice still happens in India today.