A Langa Voni (Telugu) or Pavadai Daavani (Tamil) or Langa Davani (Kannada) is a traditional dress worn mainly in South Indian young girls between puberty and marriage. It is also known as the two-piece saree or half saree.

It comprises a Langa or Paavadai, a skirt which is tied around the waist using string, and a Voni, Oni, or Davani, which is a cloth usually 2 to 2.5 metres in length. The voni is draped diagonally over a choli (a tight fitting blouse, same as worn for saree). A variant of this is the Gagra choli of North India (the difference between the two being the direction of draping the voni or dupatta).

source: http://en.wikipedia.org/wiki/Langa_Voni