Chapter four of Natyashastra, TandavaLakshanam, is one of the most important chapters for the study of dance. It is here that Bharata describes Tandava Vidhi, the rules of dancing Tandava.
The rules are in the form of long descriptions of 32 angaharas and 108 karanas, and how these body movements and postures are to be used to choreograph a performance of Tandava.
The dance was first performed by the Apsaras and Gandharvas in heaven. Later was passed to humanity through the descendants of Bharata Muni.
A Karana in dance is defined as "the coordination of the movements of the hands and feet “. Karana is a combination of three elements, namely nritta hasta (dance movement of the hands), sthaana (a dance posture for the body) and a chaari (a dance movement of the leg).
Angahara is the combination of many Karanas, while Adavus is a small unit of Karana.
A series of Karanas(subtle hand and feet movements in a spiral fashion) is called as Angahara.
Adavus are smaller units of Karana which can help you to stitch 2 Karanas in the dance. In-between 2 Karanas you can perform small steps called Adavus which is derived from Karanas. Adavu = 1 dance unit of Karana.
The 108 Karanas constitutes the Tandavam. Gentle and graceful form of same 108 movements is called Lasya. Lasya literally translates to beauty, grace, and happiness.
Both Tandavam (sharp and forceful movements) and Lasya (soft fluid movements) together constitutes Bharatanatyam.
Infact Bharatanatyam, Kuchipudi, Kathak, Odissi ,Kathakali ,Mohiniyattam and Manipuri are all offshoots of the same underlying principle