Nine Goddesses of Navratri are collectively known as Navdurga and are mentioned in the Devi Mahatmya and Durga Saptashati. The Nine Goddesses worshipped on each nine-day of Navaratri are incarnations of Goddess Shakti. Have a look on each Goddess to be worship each Navratri-
Shailaputri
'Shail' means mountains and 'Putri' means daughter. She is also known as Parvati or Hemavati. Shailaputri is believed to be the rebirth of Sati, the daughter of Daksha and the wife of Lord Shiva. In her second birth she is Parvati, the daughter of Himalaya and later she became the consort of Shiva. This is one of the very first forms of Shakti and is closely associated with Lord Shiva.
Maa Brahmacharini
Here Brahma means 'one who constantly meditates on the Supreme Being'. Brahmacharini is highly pious and is a peaceful form or is in meditation. She is also known as Tapashcharini, Aparna and Uma.
Chandraghanta
Her name Chandraghanta comes from the crescent moon worn by her on the head. This is a terrible aspect of Goddess Shakti and is roaring in anger. This form of Durga is completely different from earlier forms and shows when provoked she can be the terrible or malevolent.