Durga meaning "the invincible"is the principal form of the Goddess, also known as Devi and Shakti in Hinduism. For Shaivas and Shaktas
Durga is the wife of Shiva. For Vaishnavas Durga is another name/form of Uma or Parvati. This is especially prevalent in the Shakta denomination
within Hinduism, which worships the Goddess Devi in all her manifestations. She is Goddess Lakshmi and Goddess Saraswati in her mild form;
Goddess Kali and Goddess Chandi in her wrathful form. She is the intelligence in all beings and is referred as Chamundhaye. Durga is also
called Padmanabha-Sahodari and Narayani, the sister of Lord Vishnu. To bring back lord Shiva in Sansar, she was reborn in human form (Sati and Parvati)
to marry Shiva. Durga gave birth to her first child Kartikeya.
Origins and development :
Ramprasad Chanda writes the following about the development of Durga from primitive goddess to her current form:
"...it is possible to distinguish two different strata – one primitive and the other advanced. The primitive form of Durga is the result of syncretism of a mountain-goddess worshiped by the dwellers of the Himalaya and the Vindhyas, a goddess worshiped by the nomadic Abhira shepherd, the vegetation spirit conceived as a female, and a war-goddess. As her votaries advanced in civilization the primitive war-goddess was transformed into the personification of the all-destroying time (Kali), the vegetation spirit into the primordial energy (Adya Sakti) and the saviouress from “samsara” (cycle of rebirths) , and gradually brought into line with the Brahmanic mythology and philosophy."
The delusion of the supreme soul is otherwise called Shakti (power). From this power, generates all forms of knowledge of the world and it is accepted as vital cause of creation, existence and destruction. According to 'Shree Durga Shaptshati- Rahasyam', the original power is Mahalaxmi that created three pairs of Supreme Powers. They are Brahma, Vishnu and Shiva as male and Saraswati, Laxmi and Parvati as female, and they married respectively. Maha Saraswati is well known as Brahmani, Mahalaxmi as Vaishnavi and Mahakali as Maheswari. Durga Shakti is the original cause of all the present or past worldly occurrences. Durga Shakti is called as Adhyashakti, Paramatma Shakti or Ati Prakrutika Shakti. She is creating and controlling other two powers: Natural and General. Natural Power is called as Atma Shakti, Prakrutika Shakti, Pancha Mahabhuta Shakti etc. This Shakti creates and controls the General Energy. General Energies are called Jada Shakti or Tamashakti. By the blessings of Durga Shakti, the mother of the Universe, man is able to get his emancipation or salvation and indulge in enjoyments in performance of his daily activities.