Durga is perhaps the most widely worshiped deity of Shakti. Maa Durga's divine characterization include entire Devibhagavatham is dedicated to her. Durga means one who is difficult to approach. However since she is the mother of universe she is the personification of tender love, wealth, power, beauty and all virtues.
During Durga Puja, God in the form of the Divine Mother is worshiped in Her various forms as Durga, Lakshmi and Saraswati. Though the Goddess is one, She is represented and worshiped in three different aspects. On the first three nights of the festival, Durga is worshiped. On the following three, Lakshmi and then Saraswati Devi on the last three nights. The following tenth day is called Vijayadasami.
Vijaya means "victory", the victory over one's own minds that can come only when these three: Durga, Lakshmi, and Saraswati are worshiped.