Vedanta: Vedas, Upanishads,

Vedanta:
Collective name for the Upanishads that come at the end of the Vedas. The Upanishads deal with the ultimate reality and source of creation (Brahman). The relationship between the individual, creation and creator are represented at different levels by the many schools of Vedanta such as absolute oneness (advaita), qualified oneness (vishishtadvaita), and duality (dvaita), etc.

At a phenomenal level, there is difference; at a transcendental level, there is unity-cum-difference; and at the absolute level, there is only non-difference. Knowing this oneness and living in the harmony of the universe liberates one from the fear of sorrow, birth and death.

Vedas:

Revealed knowledge gathered (heard) by ancient sages and compiled into 4 volumes viz. Rik, Yajus, Sama, and Atharva.
The Vedic chants were memorized and passed on from teacher to student orally over a period of 5000 years. They consist of mantras or invocations to the Vedic deities, description of elaborate rituals to appease the deities (brahmanas), contemplative meditations (aranyakas), and teaching of ultimate realities (Upanishads).

Anta:

The end. Generally the end of a discussion, life, etc. Vedanta refers to the Upanishads which come at the end of the Vedas. Anta also means the purport or essence as in Siddhanta (end achieved).

Upanishads:

Name given to the philosophical discussions that come at the end of every Veda. The word Upanishad means ascertained (‘ni’ nishchaye) knowledge of the self that is most near (‘upa’ sameepe) which destroys ignorance, releases bonds of sorrow, and leads us to the ultimate reality (‘sad’ avasaadane, visharane, gatau).

The word Upanishad also is understood to mean ‘approaching, bowing and sitting’ (at the teacher’s feet). The discussions are in the form of a dialogue between teacher and student and deal with the secret (rahasyam) of ultimate reality.

There are over a hundred Upanishads of varying lengths, ten selected upanishads Isha, Kena, Katha, Prashna, Mundaka, Mandukya, Aitareya, Taittireya, Chhandogya and Brihadaranyaka are usually studied in detail.