The festival marks the occasion of Lord Rama and his brother Lakshmana approaching Mother Durga asking for her blessings in their attack on the demon Ravana.
It is significant that the Lord invoked the blessings of the divine mother, Goddess Durga, before actually going out to battle. In burning the effigies of the demon Ravana who was slain by Lord Rama it is also symbolic for us that we, the people are asked to burn the evil within us, and thus follow the path of virtue and goodness, bearing in mind the instance of Ravana, who despite all his might and majesty was destroyed for his evil ways.
Ravana was a great scholar and an ardent devotee of Lord Shiva, but the very powers that were bestowed on him for his steadfast devotion proved to be his undoing, due to his gross misuse of the same. Furthermore although empowered by his austerities performed to Lord Shiva, his powers were ineffective over the powers of Lord Rama.
Srila Prabhupada comments as follows in a lecture:
Srsti-sthiti-pralaya-sadhana-saktir eka chayeva yasya bhuvanani bibharti durga [Bs. 5.44].
This durga power is there. You have seen the picture of Durga. She has got ten hands and different types of weapons. Now the Durga-puja will be performed. You can see the Durga deity. So ten hands, the material nature. Ten hands means ten directions: north, south, east, west, and then the four corners, eight, and up and down. So ten directions. So this material nature, Durga, is controlling the whole universe, ten directions. Srsti-sthiti-pralaya-sadhana-saktir eka [Bs. 5.44]. Eka. Chayeva. But how she is working? Not independently.Srsti-sthiti-pralaya-sadhana-saktir eka chayeva. She is working just like shadow. The original body and the shadow body, they are two different. But the shadow body moves if the original moves. So therefore this word is used, chayeva. This vast power, material nature... It is a very powerful... Srsti-sthiti. It can create; it can destroy. At any moment, if there is some earthquake, the whole sea water may come and cover the land portion, and within the sea you can see one island has come out. Everyone has got this experience. So srsti-sthiti-pralaya. One side, pralaya; one side, creation. So this can be done by the material nature. But how she is working? She is working under the direction of somebody else. That is Govinda. And Govinda also says in the Bhagavad-gita, mayadhyaksena prakrtih suyate sa-caracaram: [Bg. 9.10] "She is working under My direction."
So far killing or destroying is concerned, that Durga power, Krishna’s power, that is sufficient. He doesn't require to come to kill the demons. She is engaged. You have seen that Durga is killing the demon, that asura. You have seen the Durga's picture? The asura is there and the lion is there, and she has taken a bunch of hair of the asura, and the trident is pushed on his chest, and the lion has captured him. So he is overpowered. So the asura is overpowered, but if the asura makes more attempt to save himself, then there are, only two hands are engaged of Durga to kill the asura, one catching his hair and one the trident. Only two hands are engaged. But if he shows more power, then there are eight hands more, reserved with different types of weapons. So you cannot overcome the ruling, or the control, of the material nature. That is not possible. Daivi hy esa gunamayi mama maya duratyaya [Bg. 7.14].
- Srila Prabhupada lecture, Sept. 30, 1974, Mayapur