Durga is worshipped during Navaratri. These are Shailaputri, Bramhacharini, Chandraghanta, Kooshmanda, Skandamata, Katyani, Kalratri, Maha-Gouri, and Shidhidatri.
The first day of Navratri is dedicated to Goddess Shailaputri. The second day of Navratri is celebrated to revere Goddess Brahmacharini. The third day for Goddess Chandraghanta embodies fearlessness and courage.The fourth day of Navratri is dedicated to Goddess Kushmanda who resides in the abode of the Sun God. Fifth day for Skanda Mata, Moksha or salvation can be achieved by worshipping Skanda Mata. Goddess Katyayani is revered on the sixth day of Navratri. On seveth day for Goddess Kalaratri rides a donkey and is considered the most aggressive and destructive manifestation of Durga. The eighth day of Navratri is dedicated to Mahagauri who washes away the sins and bestows her worshippers with success and prosperity. The ninth form of Durga, Siddhidayani or Siddhidatri is the Goddess of wisdom. On Vijayadashami day all nine form of goddess combines together and became powerful Durga to defeat the Mahishasura.
Source: http://in.lifestyle.yahoo.com/nine-forms-durga-183009715.html
Wish You All A Happy & Prosperous Durga Puja