The following is excerpted from an article on  the Belur Math Headquarters web site:

 

Navaratri and Durga Puja

 

The nine days from the first day after the new moon (known as Mahalaya) in the Indian month of Ashwin to the 9th day constitute the festival of Navaratri which is observed all over India.  During this period, the Divine Mother is worshipped in some form or other.  The majority of Hindus who cannot conduct such worship at home visit Mother's temple in their locality after taking bath and putting on new clothes.  The tenth day is known as Dassera.  In the northern parts of India, on this day the life of Rama (known as Ramlila) is enacted in public.  In many parts of India, on this day weapons, implements, instruments, etc are worshipped.  [In Bengal, this worship of tools and implements takes place on another special day known as Vishwakarma Puja.]

 

It is during this period of Navaratri that Durga Puja is celebrated in Bengal.  The celebration of Durga Puja is a unique feature of the socio-religious culture of Bengal.  In no other part of India does the worship of Durga affect the lives of the people so deeply as it does in Bengal.  Festivities begin from Mahalaya and go on for nearly a month.  During this period, people put on new clothes, worship the Divine Mother at any of the beautiful Durga pandals put up in different parts of the city or town, and enjoy feasts. 

 

The most striking aspect of Durga Puja is the image of the Divine Mother as Mahishasura-mardini.  Here the Divine Mother is seen as having ten arms, each wielding a weapon.  [Hence She is described as Dasha-prahara-dharini.]   Once the image is consecrated, and the Deity is invoked in it, it undergoes a transfiguration.  It is no longer a clay image but the living Goddess, radiating power, knowledge, love and joy, the benign Mother of the Universe who has come to bless Her children and to assure them of Her love, help and protection.

 

Another prominent feature of Durga Puja celebration is the gorgeous Pandal or Durga dalan in which the worship is conducted.  Durga Puja is meant for public worship, in which a large number of people participate. Its rituals and paraphernalia are quite expensive.  Formerly only kings and aristocratic families could afford to celebrate such public worship.  But in modern times Durga Puja is done through organized community effort.  People of a locality or street form a celebration committee, take collections and put up the imposing pandal.

 

Who first started this kind of public celebration of Durga Puja?  Sri Durga is a Vedic deity as we find mentioned in the Vedas. The worship of the Divine Mother used to be performed in spring as Basanti Durga Puja. Sri Ramachandra performed the worship of the Divine Mother in fall and called Sharadiya Durga Puja. Then onward this puja was performed all over the India. In Bengal, it accepted view is that it was Kangsa Narayan, king of Taherpur in Rajshahi District (now in Bangladesh), who first started the present style of public celebration of Durga Puja around the year 1606.