The Durgati Nashini maa Durga's 9 days of Navratri has started. These 9 days are celebrated to worship all the 9 major Avatars of maa Ambe. According to a vedic theory Lord Brahma gave these specific 9 names to different Avatars of Goddess Durga according to her work.
So the 9 Avatars are:–
Mata Chandra Ghanta
Mata kaal ratri
Mata Maha Gouri
Mata Siddhi Datri
All the Avatars taken by Mata Parvati. Are due to some significant roles and purpose.
Maa Sailaputri - The King of Himalaya Shail got Maa Durga as her daughter. And by his name ,maa Durga was named Sailaputri. She was also called Devi Parvati or Devi Hemabati.
In her previous birth she was the daughter of Prajapat Daksh(son of Brahma) ,her name was Sati, she too married to god Shiva. But she left her body by going into fire in Yajna arranged by her father. Her pet was cow and she holds a trishul in right hand and a lotus in left hand.
Maa Brahmacharini - Brahma means Tapasya ( meditation) . And Brahmacharini means tapaswini. When Devi Parvati(Sailaputri) knew that her destiny is to marry Lord Shiva. She started Tapasya for him to convince him to marry her for more than 1000 years. This type of Tapasya was very difficult at that time that's why she was named Brahmacharini. She hold a necklace of Rudraksh and a Kalash in her hands.
Mata Chandra Ghanta - In this Avatar of Devi Durga there is a moon that looked like bell on her crown. That's why she was called Chandra Ghanta. In this Avatar she rides on Tiger. She have 10 hands. With hands holding weapons like, Sword, trishul,gada, axe, bow, arrow, bhala. And other 3 hand are to give blessing , hold lotus and Kalash. In this Avatar Devi Durga killed Mahisya asur.
Devi Kushmanda - According to vedic theory when ther was nothing in universe not even a star . There was a big ball of gasses and maa Kushmanda burst it by which the universe produced. She lived in sun so her temperature is same as sun. Due to her reflection there heatness of life in everyone in the earth. She too rides on tiger and had 8 hands. With holding Shank, chakra ,gada , Padma,Dhanush ,tree, Kalash , necklace of Rudraksh and posture of blessings. That's why she was also called astabhuja.
Skandamata - She is the mother of Skand means Kartikeya. That's why she was called Skandamata . Skandamata rides on lion and has four arms for holding baby form of god Skand(Kartikeya) in upper right hand, giving blessings in upper left hand. And holding 2 lotus in both lower hand.
Mata Kaal ratri - In this Avatar of maa Parvati her body colour is totally black. She rides on donkey. With disturbed hair. Maa Durga uses this Avatar if she gets much angry or if she have to save her family. But to revive her to normal is very hard. She will get normal only if she gets emotionally touched. She has 4 arms 1 for axe, 1 for 6 pointed sword, one plate to store blood and one give blessing. She also blow fire through her nose. She looks very dangerous. Demon, devil,evil, ghost all scares and goes away listening her name.
Maa Katyaini - She took birth in Rishi Katya's house. She rides on Tiger. She has 4 arms . She hold chakra, sword, lotus and give blessing.
Maa Maha Gouri - when in form of Sailaputri lordess Durga meditated for Lord Shiva. Then Lord Shiva accepted her devotion but due to years of hardwork her colour has turned Black so lord Shiva told her bath with Ganga water. Then she turned to talk fair (Gouri) . She wears white saree with white marble necklace, white chakra. She rides on white Ox. She holds Damru,trishul,white Jasmine and give blessing.
Maa Siddhi Datri - Maa Siddhi Datri hold all Magical powers. By her powers she joined herself with lord Shiva and were called together Ardhanariswar.