Sharad navrAtri is celebrated in the Rtu (bimonthly season) of sharad (comes in September/October), and it is the first nine nights (nava=nine, rAtri=night) of the shukla paksha (bright fortnight of the month when the moon is waxing) of the ashvin or Ashvayuja month (month of ashvin). During this period it is easiest to have a direct experience of the power of the Divine Mother who is worshipped in the form of DurgA, LakshmI, and SarasvatI. Usually of the nine nights, three are dedicated to each of these forms. Of course, mA Shakti (mA=mother, shakti=power), is also worshipped as PArvatI, GAyatrI, BhavAnI, etc. Her forms are many but she is the same.
I'll first try to describe to you the importance of understanding mA Shakti as DurgA. The word DurgA means 'hard to go to', or 'hard to attain'. Although mA Shakti is the cause of everything and is everywhere, she is hard to see or attain. This is because mA Shakti, who is also mAyA (mA= not, yA=this), conceals or covers up Her true nature that is in everything through Her power (shakti). Her shakti has three aspects: (1) vikshepa shakti, (2) AvaraNa shakti and (3) jnAna shakti. Let us try to understand what these three aspects of shakti are.
(1) Vikshepa shakti comes from the Sanskrit root verb (kship=to throw) and it is the projecting power of mAyA. Just as the film projector in a theater casts entrancing and captivating images on the white projector screen, the vikshepa shakti of mAyA creates this world for us. And it is as captivating as an exciting movie into which we get deeply engrossed while we are in the theater.
(2) The second aspect of her shakti is AvaraNa, which means 'covering up' or 'veiling', coming from the Sanskrit root verb (vR=to cover). It is this aspect of her shakti that does not permit us to see her for what she really is. Just as we do not see the white projector screen for what it is when the movie is playing in the theater, but instead we see the colorful images that appear so real to us, so also we do not see shakti in the external world. This happens because we usually only perceive the world through our five senses that respond to the five mahAbhutas (pRthvI, apah,agni,vAyu and AkAsha). Through dhyAna (yogic meditation), prayer or bhakti it is possible to see through this veiling power of mAyA.
(3) Through the third aspect of her shakti called jnAna shakti, the merciful Divine Mother saves us. jnAna means wisdom, and here it means a very special kind of spiritual wisdom or brahmavidyA. It is the knowledge of the real nature of things, of Brahman, and it is mA Shakti who is the path to this knowledge. So when you sit in prayer these nine nights of sharad navrAtrI, for the three nights that are dedicated to DurgA you will know the true meaning of her name. We adore her for her great power in projecting this wonderful world, but most of all we pray for her to light the lamp of wisdom within us so that we may see her in her true form.
In the first three days of the navrAtrI (prathamA, dvitIyA and tRtIyA), devI is easily seen as durgA (of course durgA means she who is hard to get to, so this requires sAdhanA or devotion to devI). As durgA she represents the form of devI who destroys tamas, and she helps overcome the power of tamas. She cleanses the cakras in the mUlAdhAra and svAdhishThAna (where tamas is predominant) and raises the jIvA's consciousness to the level of maNipUraka cakrA (in the navel). The color of the devI is dark and black in the first three days.
In the next three days (caturthI, pancamI and ShaShThi) She is seen as lakshmI. She helps overcome the power of rajas. She cleanses the cakras in the maNipUraka, anAhata (where rajas is predominant) and raises the jIvA's consciousness to the vishuddhi cakra. The color of the devI is red and represents rajas in the second three days.
In the last three days (saptamI, aShtamI and navamI) She is seen as sarasvatI. She helps overcome the power of sattva. She cleanses the cakras in the vishuddhi, and AjnA (where sattva is predominant) and raises the jIvA's consciousness to the sahasrAra cakra. The color of the devI is white and represents sattva in the last three days. On saptamI, devotees invoke the devI as sarasvatI and it is called saravatI AvAhanam.
The significance of vijaya dashamI is the conquest of the ego and the melting of the jIvA into the paramAtma, although they were never different to begin with. It is the end of avidyA. It is indeed a great spiritual victory and conquest of the demons of the senses and ego.
May your mind be ever turned towards devI who is the only One Reality, who through Her infinite Power appears as many.
"Worship devi in navratri as body tamas durgA, mind rajas for it emerges lakShmi and buddhi sattva Saraswati." The following explains this rather cryptic sentence.
Worship Devi in the navratri in the first three nights as the body- the physical manifestation, in the cakras mUlAdhAra and svADhiShThAna, in Her tamasic aspect as durgA. DurgA is She who is hard to attain. Her shakti is AvaraNa shakti or the power to veil and cover the Truth. Her color is black and her Power destroys the aspects of mind that lead to ignorance in those cakras- specifically She destroys fear of loss of the physical manifestation (body) and She helps overcome desire.
For the next three nights She is worshipped as the mind which is her rAjasic aspect, for it emerges and represents Her vikshepa shakti. She is worshipped as LakShmi and clothed in red colored garments. She overcomes ignorance in the maNipUraka and anAhata cakras. These lead to great strength and opening of the heart to compassion and understanding.
For the last three nights She is worshipped as buddhi, the discriminating intellect, which is sAttvic in nature. Her shakti is jnAna shakti here. Her sAttvic nature is Sarasvati and Her color is white. She is worshipped in the vishuddhi and AjnA cakras. She gives divine speech and spiritual knowledge.
On Vijaya dashami She is to worshipped in complete silence in her nirguNa aspect at the sahasrAra cakra. There is no color, or sound or guNa here.