Navratri is a nine-day Hindu festival, celebrated by many devottees all across India. The festival is dedicated to worship the Hindu deity Durga.
One out of nine avatars of goddess Durga; be it Maa Shailputri, or Maa Brahmacharini, or Maa Chandraghanta, or Maa Mahagauri and so on is worshipped each day. But the ninth day of Navratri is dedicated to Maa Siddhidatri. She has the power to fulfill all the wishes of her devotees and those who pray to her, get relief from all their sufferings.
Many devotees fast for entire nine days during the festival. They chant various mantras and slokas while worshiping the deity.
On the ninth day of Navratri, Goddess Siddhidatri is worshiped. Siddhi means meditative ability and Dhatri means giver. She is seated on a lotus and has four arms which hold a lotus, mace, conch shell and discus. This day is also observed as Mahanavami. As per Hindu mythology, Lord Shiva had attained all the siddhis by the grace of Goddess Siddhidatri and this is the reason why his half body was that of the Goddess; he was known as Ardhanareshwara.