It's 2007 Durga puja time. Celebration of famous victory of Hindu goddess over demon "Mahishasur" and subsequent (Many years later) victory of Rama over Ravana.
Bengali people celebrate the first victory while rest of the india celebrates the later.
Who was Mahishasur? He was the non-Aryan ruler of great indian planes. If you ever come from Afghanistan and Iranian border (by land of course) that would be first thing you would notice in the north India is the vast plains. In the early days of Aryan settlement/invasion, they had encountered stiff resistance from Native non-Aryans. In spite of these battles, the green pastures of Indus and Ganges basin looked alluring to the Aryans; the harshness of Asia-minor and Afghan terrain made their little settlements look like heaven.
To the native non-Aryans this called for a struggle for existence, they were civilised society who could build cities like those found in Indus valley civilisation. One of the major differentiators between these two societies was their cattle. The Aryans are known for their long association with the cow and the non-Aryans were buffalo herding people.
Wild buffalo were abundant in the plains, you can find their reference in Indus valley as well as Aryan Puranas. Mahisasur were king of the grazing territory with his huge herd of buffalo's. His tribe had domesticated some buffalo's and even rode on them during raids on Aryan settlement (sometimes referred as heaven).
In the fight for the grazing land (which when took place in the long grassy patches specially after the monsoon) the buffalo's were quick and deadly ride. So Mahisasur struck awe and terror in the minds of early Aryan settlers (Or call them gods if you like).
Who was the goddess Durga? Who were the other gods who defeated by the Mahishasur? Contrary to popular belief, the early Asian settlers were not single pure race. The gods as we know them in Hindu mythology, were actually fractured tribes, some what loosely governed by an Aryan super council. Brahma the most righteous of the tribes gave rise to all other tribes or Gods. Bishnu / Narayana represented the most prosperous trading tribe. Henceforth in different purana (ancient folklore) you get different relationship/affinity/bonding between hindu gods/goddesses, which actually represented important trading and other socio-economic links between tribes.
It is told in numerous occasion in puranas, the gods had reincarnated in different avtaars, which is nothing but a resurgent tribe under a new leader, probably bringing a new victory or glory to the clan in similar troubled times.
So back to the question of Goddess durga? She is the wife of God Shiva and daughter of Himalayas ( The Mountains). Shiva is the oldest God and was not originated from Brahma and does not get glorified in the folklore in spite of numerous victories. He is also known to have had turbulent relationship with other gods and had defeated them in battle several times. His followers were ghosts and other lost souls in the himalayas.
The important factor is that he does not originate from brahma makes him non-Aryan but possibly native like the asuras. Shiva was the astute tribe that got included in the Aryan line because of heavy intermix with Aryans and their prowess in the field of war.
Besides the leadership of shiva the rest of his followers do not glorified in the folklore, he is known to have blessed other asuras too. So this tribe have had the skills of training other tribes in the arts of ancient war.
So Durga was the an army of soldiers lead by Female warriors recruited from the foothills and trained by shiva. The Idol of durga rides tiger/lion , which means they had taken the herd of buffaloes to the patch of land where the big cats had taken many buffaloes out. With depleted ride and cattle the asuras fought hard. Goddess Durga is known have ten hands and they are loaded with ten weapons/utilities from ten gods. It is clearly stated that she had used one weapon after another. These arm and armoury represent small and elite troops from ten different tribes, under the command of Goddess (Lady general who incidentally was married to the chief of the shiva tribe). So this war was a classic case of a group of tribes coming together to form a coalition of force and a highly technical war.
Now that you have human explanation of things mentioned in the purana, go enjoy the puja. One last thing, worship of a god in past actually means training or research under the chief or other elders of the tribe.