Moksha is a term used in Hinduism which refers to liberation, enlightenment, and release. It is a state where one gets complete freedom from Samsara, from the cycle of death and rebirth. It also refers to a state where one gets liberation from ignorance.
The Upanishads are one of the most important religious and philosophical texts of the Hindus. They were written somewhere between 1500 BCE and 1000 BCE during such times when the Indian society started to raise their doubts about the traditional Vedic practices. The post offers you a detailed and insightful summary of the Upanishads.