Upavedas are subsidiary areas of knowledge in the Vedic scheme (viyasthana). Upavedas form what is known as vidyasthana (seats of knowledge) consisting of eighteen disciplines of knowledge (ashtadasa vidya). The first fourteen are directly concerned with dharma.
Upavedas do not directly deal with dharma. Vedangas and Upavedas are described as Shastra commandments.
Upavedas are four in number. Ayurveda is the upaveda of Rig Veda; Dhanurveda is the upaveda of Yajurveda; Gandharva Veda is the upaveda of Samaveda; Arthveda (Arthashastra) is the upaveda of Atharvaveda.
Upavedas are different from the six Vedangas, which are considered necessary for the study and understanding of the Vedic mantras.
Upavedas are so called because their main philosophical tenets are related to main Veda.
Ayurveda deals with all aspects of total health. It is a science of life or medicine. The founder deity of Ayurveda is considered to be Dhanvantari. Charaka and Sushruta are great names associated with this science of life.
Dhanurveda is the discipline which deals with the mystic missile technology and all related issues, specifically archery and use of weapons for defense and offense.
Rudra is considered to be the main deity of Dhanurveda.
Gandharva Veda deal with the fine arts needed for emotional refinement. Bharata Muni, the composer of Natyashastra (treatise on dramatic composition and performance), is the name to be reckoned with here.
Arthashastra deals with the management of the resource of life and wealth. The names associated with Arthashastra are Brihaspati, Shukracharya and Kautilya (Chanakya).
Natyashastra, insofar as it deals with music and dance, is related to Samaveda, acting to Yajurvea and aesthetics to Atharva Veda. The four Vedas thus form the main source of all knowledge.
Source – Encyclopedia of Hinduism Volume XI page 56-57 - IHRF