Navratri is the worship of the feminine. In our Hindu culture, we worship the three forms of femininity; Durga, Laxmi, Saraswati. These three devis represent the three forms of the divine. Durga is the representation of the earth and for those who seek strength and power, they turn towards Durga. Out of the three gunas Sattva, Rajas, Tamas, Durga represents the Tamas guna. It signifies inertia and is associated with forms of the feminine like Mother Earth or Durga or Kali.
Laxmi is the second form of the feminine. She is symbolic of the sun and Rajas guna(activity or passion). The people who seek wealth and material happiness, worship Laxmi or the Sun. Saraswati is the representation of the moon and is associated with the sattva guna(Purity and transcendence). She makes one knowledgeable and transcends them from this worldly dimension to the dimension within.
The nine days of Navratri are the worship of these three forms of the feminine. The first three days are for the worship of Durga or the Earth. The next three days are for the worship of Laxmi or the Sun and the last three days are for the worship of Saraswati. In the life of a human being before he is born his life is governed by the Tamas guna. Inside the womb, it is a state of inertia. We originate and reverberate. We keep growing and come to life. At the time of our birth we get into rajas. Our activities start and we start to function. These two forms of the devi are necessary for the human survival but the third dimension, the dimension of Saraswati is the one which liberates you from the cycle. It is the aspiration to go beyond the life and death and the mortal bodily functions.
In Navratri these three forms are worshiped by those who aspire to be more. The tenth day, the day of Vijay Dashmi signifies the triumph over all these three aspects of life.